With some of the world's finest street food, ancient ruined temples amid rainforest and beaches of almost surreal beauty, the Southeast Asian country is a feast for the senses.

Cover the entire length of Thailand by car, taxi, plane and longtail boat, beginning in Bangkok, then heading north to the ruins of Sukhothai and hill villages of Pang Daeng Nai, before darting south to the limestone-karst landscapes of Khao Sok and Ko Hong.

Bangkok: Best for street food
The queue of hungry people can barely be seen behind the smoke and steam rising from the boiling pans and spitting grills of the street stall. Three men work furiously, serving up bowls of a hot, peppery Thai pork broth called kuay jap nam sai, one of Bangkok’s most popular dishes. Its spicy tang floods the air, mixing with the scent of roasted nuts being stirred by an elderly woman and the sweetly rotting smell of a spiky durian fruit being cut with a hatchet.

Tucking into a plate of cooked-to-order noodles or skewers of sizzling meat is a daily ritual here. It seems that every street corner has at least one vendor, their charcoal grills and scorching woks hissing with stir-fried vegetables, charred meats, pungent spices and delicate sweets. And while money can buy you a lot of things in Bangkok, it can’t help you jump the queue: street cleaners and market traders patiently line up alongside office workers and suited financial whiz-kids. ‘I’ve been here for 30 minutes,’ says one man, glancing at his watch. ‘But it’s worth the wait.’ His turn finally arrives, and he grabs his steaming bowl of soup, ladles green chilli and garlic sauce on top, then squeezes onto a packed bench and takes up his spoon.

There are food stalls around Victory Monument and busy Charoen Krung Road, but it is in Chinatown’s tightly-knit maze of narrow streets where Bangkok gathers when its collective belly rumbles. Here, Thai vendors dishing out green and red curries or flat rice noodles with meat stand shoulder to shoulder with cooks from the city’s Chinese population, serving dishes such as bird’s nest soup. Barrow boys wheel carts of oranges between rows of bubbling cauldrons and tables piled high with spring rolls, chicken kebabs and coconut jellies.

The most famous Thai dish – pad Thai, a sweet and spicy combination of stir-fried shrimp, lime, peanuts and noodles – originated on a nearby stall called Thip Samai. Here, a local woman (after whom the stall was named) invented the dish during WWII, when the government was encouraging people to cook with local ingredients. Today, what was once a simple roadside set-up is an established restaurant with a street stall attached, run by Thip Samai’s grandson, Sikarachat Baisamut. ‘My grandmother came up with the recipe, my mother tweaked it, and now I don’t have to do anything,’ he says. He’s worked on the stall since he was a teenager, and has witnessed his grandmother’s recipe become the unofficial Thai national dish.

The stall is a hive of activity: woks filled with noodles, shrimp and spring onion are expertly tended. Plate after heaped plate is served up to hungry customers. ‘I’m happy that everyone wants to cook pad Thai – it’s good to make Thai food popular. But I’m not worried about the competition,’ says Sikarachat. ‘Other people use the same ingredients but create something very different – no-one can make it with the pride and love that we do here. Cooking Thai food is like making a work of art.’

Sukhothai: Best for ruins
Each of the Buddha’s long, tapered fingers is the size of a man. They rest on his gigantic right knee, close to the temple floor, while his other hand lies upturned on his lap. His face is beatific, his ear lobes dangling almost to his chin. Two Thai visitors enter the walled shrine and kneel before the vast deity. One lights the end of an incense stick and bends low to the ground in prayer. The other places a small square of gold leaf on the Buddha’s index finger, glittering in the late afternoon sunlight. The great fingertip is now almost entirely covered in gold, thanks to legions of pilgrims who have visited this place: the ancient temple site of Wat Si Chum, in the ruined city of Sukhothai.

The site is now a green swathe of national park, set amid the paddy fields, stilt houses and lotus-filled lakes of central Thailand. But the 200-odd ruined temples and statues that are scattered here testify to its former glories. From the 13th to the 15th centuries, Sukhothai was the capital city of what was then known as the Kingdom of Siam – and the cultural, architectural and educational achievements made during that short period continue to resonate today.

Chaiwat Thongsak, assistant director of the Ramkhamhaeng National Museum at Sukhothai, gestures to the giant Buddha, explaining that people come to stick gold leaf onto the statue’s hand in the hope it will bring good fortune and wealth in the coming year. ‘Thai people adore this place,’ he says. ‘We’re proud that we can trace back the history of the Thai people here, and that we have managed to protect 700 years of our heritage. Because many people believe that the Sukhothai kingdom was the pinnacle of our history and culture.’ Thai people flock here to pay tribute to the ‘Great King’ Ramkhamhaeng, who not only built most of this place and cemented Buddhism as the central religion, but also invented the curled letters of the Thai written language.

The dominance of Sukhothai gently faded away over the centuries, as people moved further south to be nearer the main waterways for trading, and the jungle began to reclaim the site. It was almost forgotten until 1953, when a wave of post-war nationalism led historians to turn their attention to the ancient capital, and the process of restoration began.

The contrast between this place and the hubbub of Thailand’s new capital, Bangkok, could not be greater: instead of crowded streets and beeping, buzzing tuk-tuks, a handful of cyclists silently ride past, and pools covered with sacred lotus flowers gently ripple in the breeze against a backdrop of stupas. The magnificent, crumbling conical towers of Wat Mahathat, the central temple complex, are decorated with intricate carvings of monks encircling the shrine in prayer. In the centre stands another statue of the Buddha, elegant and composed, sitting out the centuries as the world changes around him. ‘Sukhothai is now a place of peace and solitude,’ says Chaiwat. ‘I think it’s a feeling that will remain with the Thai people, deep down, no matter how big or busy the country gets.’

Pang Daeng Nai: Best for hill tribes
Morning arrives slowly in the hill tribe villages of the north. It takes a little time for the sun to gather enough strength to burn through the mist that rises up from the teak forests and hangs over the mountains. But as it clears, the Palong tribe awakens. Men and women emerge from their one-storey stilt homes that are clustered beside the quiet river that threads its way down from the mountain. A group of men enjoy a chat and a cigarette before heading to work on the rice terraces, while women sit shaking trays of corn to separate the grain from the chaff. Children mess around on rusty bikes, avoiding flocks of chicks that peck at any fallen kernels on the ground.

The Palong live in Pang Daeng Nai, in the low, forested hills that lie 50 miles to the north of Chiang Mai, and they are just one of more than 20 hill tribes who call the jungles of northern Thailand home – from the shamanistic Hmong people to the Lisu, laden with chains of silver. These peoples now live in hundreds of villages throughout the hills, but have traditionally belonged to no nation, in a similar way to gypsy travellers in Europe. Nomadic tribes, each with their own distinct culture, they have spent the past two centuries moving through China, India and Burma, chased by war or searching for new lands to farm, before finally settling in Thailand. Their decision to stop here is unsurprising: the land is fertile, abundant with banana plants, mango trees and vines of passion fruit, and bamboo grows fast and strong.

Kum Jongtan is the founder of this village and led his people here after war forced them out of Burma. He sits barefoot on the floor of his wooden house, beneath framed pictures of Buddhist monks, his teeth black from chewing the betel nut that is the traditional caffeine-like pick-me-up amongst the tribes. ‘We walked through the jungle for 10 days and 10 nights until we found this place,’ he recalls. ‘At first there were only 11 families, and we drew lots for where we would build our houses.’

Three decades later, the village has grown exponentially, and it now offers homestays so that visitors can meet hill tribe people, or go trekking in the mountains. Kum is glad that his tribe’s nomadic days are over – Thailand has become too built up, he says, and there is no more land to move into. ‘But Thailand is a good place to live. There is peace and there’s no need to keep moving.’

Across the road from Kum’s house, a woman named Fon Por-Tow sits on her porch, dressed in tribal finery – a startlingly bright purple and pink velvet jacket, adorned with silver coins. She pulls some purple wool from her homemade loom and begins to weave, an intricate dance of fingers and thumbs. She is making a shoulder bag, decorated with patterns that bear traces of previous generations’ travels through India and Burma. The Palong’s distinctive colours were once made using natural dyes provided by the jungle, such as the purple skin of the mangosteen fruit, but now, she says, she buys chemical dyes in Chiang Mai: it’s easier, and the colours are more vivid. In the heart of the jungle, it’s a sign of how the modern world is creeping in, but the loom still rattles as it has for generations and the people retain their traditions along with their deeply cherished independence.

Khao Sok National Park: Best for nature
The heat hangs over Khao Sok National Park like a hot, wet cloth. This is jungle country, deep in Thailand’s southern tropics, and every step along the trails that wind through the park is weighed down with a hot compress of humidity. A cool consolation is the extraordinary scenery: the primeval forests of Khao Sok, which rise and fall with the huge limestone mountain peaks that stand sheer and abrupt against the sky.

The forests are thought to be more than 160 million years old. Save for a few rubber plantations, this is virgin jungle, unaltered by human hand. The topography of the canopy, the evolutionary battle between the trees stretching to the sky, is one that has been decided by nature alone. As the path continues through the greenery, there is a sense that this is how the world must have looked before the arrival of man. Everything is supersized – copses of bamboo tower above the trails, while the fan palms are the size of semi-detached houses.

And it pulsates with life, from the twig that turns out to be a leaping insect to the ‘shy plants’ who snap their leaves shut when disturbed by wind or water, not to mention the tribes of bright beaked hornbills, gibbons, wild elephants, leopards, and millions of insects. All of these creatures combine their wing-rubbing, squawking and howling to make a constant din that has been charitably described in some quarters as a ‘jungle orchestra’ – a high-pitched drone, oscillating and reverberating endlessly. As the day slides into dusk, the bigger insects, such as the black-winged ceconda beetle, join in the chorus, and the pitch rises to that of an ear-shattering fire alarm or an industrial drill.

One man who has had plenty of time to get used to the noise is Sak Chai Paelee, a park ranger at Cheow Lan lake, a man-made lake that was created by the construction of the Ratchaprapha Dam, in the south of Khao Sok National Park. He lives alone in a hut on one of the towering limestone islands within the lake. ‘I don’t even hear the noise,’ says Sak Chai, looking out over the glassy waters to where his longtail boat is moored. ‘This is silence to me.’ Sak Chai has lived on this island for 10 years, with only a one-channel radio for company. ‘I get lonely sometimes’, he says, ‘but I enjoy a peaceful life – when I do go into town, it feels like chaos! I want to work here until I die.’

Ko Hong: Best for beaches
Each morning, Tri Rasang Kaewnui wakes up and puts the final touches to what he believes is the most beautiful beach in the world. He has worked as a ranger on Ko Hong, a collection of twelve tiny islands off the coast of Krabi, for five years and he takes his work seriously, making sure all leaves are swept from the beach long before the first tourists arrive on longtail boats, so as not to spoil the illusion of perfection. ‘Every day I wake up here, and feel so proud that I am one of the protectors of this place,’ he says. ‘People travel for miles and spend so much money to visit here – they see it as a precious stone. I get to see it every day for free! So I want to do everything I can to keep it the way it should be.’

Ko Hong’s main beach is at Ao Bo Lae, a slimline sceptre of pristine white, soft sand gently massaged by waves that don’t crash so much as murmur. A thick border of verdant rainforest rustles in the breeze, manned by a scampering gibbon or two, all backed up by towering limestone cliffs for added drama. It feels like a remote paradise, but Ko Hong is no secret – as the sun rises to its midday height, the shore begins to fill with longtail and speed boats dropping off fellow pilgrims. Thankfully the beach’s size provides a natural limit to the crowd and it retains its tranquil splendour.

Ko Hong means ‘the room’ in Thai. The name comes from an ancient legend about a woman named Phranang who hoped that this island would act as a wedding suite for her and her new husband, but he was lost at sea and she died waiting for him, broken-hearted. On another beach on the island of Railay, a 40-minute speed boat ride away, a large, deep cave cut into the cliffside is said to be the home of Phranang’s despairing spirit. The cave is packed with tributes left by local fishermen – lit candles, flowers, bottles of water and, perhaps unexpectedly, huge wooden penises known as lingams. The cave is piled high with lingams of every shape, size and colour, all the way up to a seven-foot phallus, wrapped in ribbons.

Back at Ko Hong, just around the corner from Ao Bo Lae, the otherwise continuous circle of limestone cliffs that surround the island opens up slightly. Sailing through this inlet reveals a huge freshwater lagoon, shimmering aqua green in the sun. The walls of the lagoon tower formidably above, each covered top to bottom in rainforest, which is somehow growing at right angles to the rock face – a vertical ring of greenery, hugging the water below. It is here that the love story of Phranang should have ended happily, had fate not intervened. And for those who know the tale, this gravity-defying, wondrous landscape retains a sense of bittersweet beauty, a faultless paradise somehow infused with lost love.

The article 'The perfect trip: Thailand' was published in partnership with Lonely Planet Traveller.