Ko means island in Thai, and the very word conjures up dreamy beaches, fantastic rock formations and undersea gardens. Hop in a long-tail boat and cast off the moorings.

‘Ko’ means island in Thai – the very word conjures up dreamy beaches, huts in the shade of a coconut palm, fantastic rock formations and undersea gardens. Hop in a long-tail boat and cast off the moorings.

Southern Gulf
A scuba-diving honeypot off the crystalline Gulf Coast, Ko Tao is also the easiest and cheapest spot around to learn dive basics. The Japanese Gardens, to the island’s northwest, is an ideal dive site for beginners, with plenty of coral, turtles, stingrays and pufferfish. Big Blue Diving is a recommended mid-sized local diving school (Hat Sai Ri; four-day beginner courses £185).

Fairly large and multi-faceted enough to fit in luxury yoga retreats as well as backpacker shanties, Ko Samui is particularly blessed with places to eat, not least the many kow gaang (rice and curry) roadside stalls. The town of Hat Chaweng meanwhile is home to the Samui Institute of Thai Culinary Arts, which has daily cooking courses and classes in the arts of carving fruit and vegetables into intricate floral designs (Hat Chaweng; three-hour courses £40).

Things are changing on Ko Pha-ngan. Parties still take place on the beach at Hat Rin every full moon, but the island as a whole is creeping upmarket. The beaches of the north and east are still relatively secluded (Hat Khuat, or Bottle Beach, is a top choice), and the jungle interior rewards exploration with four, year-round waterfalls. Change out of beach clothes to visit one of the 20 wat (temples) – Wat Pho, near Ban Tai, offers a herbal sauna for about £1.

Andaman Coast
The impressive limestone karst coast of Trang Province shelters several sublime islands. The isle of Ko Muk is home to spectacular Hat Farang (aka Hat Sai Yao) – a calming stretch of sand where jade water kisses a perfect beach. Further north, Tham Morakot (Emerald Cave) is a rock tunnel leading – at low tide – to a small beach surrounded by cliffs on all sides.

One of the most unspoiled regions in all of Thailand, this park encompasses 51 islands, including Ko Tarutao itself, covered in old-growth jungle. Long-tail boat tours take in islands home to hornbills, langur monkeys and fishing cats. Ko Lipe is the most developed island, but also has the widest choice of accommodation and beautiful beaches.

Ko Lanta is a crucible of cultures, mixing Buddhist temples, slender minarets and chow lair (sea gypsy) villages. Northern beaches are busy but fun, with more mellow ones to the south. The cave complex of Tham Khao Maikaeo conceals a subterranean pool and chambers as large as cathedrals – local guides can arrange treks (around £4), and resort hotels can arrange transport and motorcycle hire.

Northeast Gulf
Within weekending distance of Bangkok, Ko Samet is popular with Thais and visitors alike, but is surprisingly underdeveloped all the same. A coastal footpath runs the four-mile length of this skinny island, skirting one lovely cove after another. Sunset at the northern end brings late-night parties and karaoke sessions; things get quieter the further south you go.

With steep, jungle-covered peaks erupting from the sea, Ko Chang retains a rugged spirit despite its package-holiday reputation. This is largely down to its accessible wilderness: island treks allow you to explore forests filled with birds, monkeys, lizards and beautiful flowers. Evolution Tours offers one-day trips that include a waterfall swim and a stop at an elephant camp (treks from £28).

Coconut palms outnumber buildings on Ko Kut, just 20 miles by sea from Cambodia, where a secluded, unhurried atmosphere pervades everything. There’s not much nightlife or even dining, but the beaches of the western side, Hat Khlong Chao above all, are among Thailand’s finest. Two inland waterfalls are good short hiking destinations, with pools to cool off in.

Where to stay
Lemon yellow bungalows sit peacefully beside the sea at Ko Chang’s KB Resort. Listen to the lapping of the surf while kids construct mega-cities in the sand. Go for an air-conditioned villa if possible (10/16 Moo 4; from £30).

Sri Lanta is a decadent yet ecologically responsible resort on Ko Lanta where naturalistic wooden villas dot wild gardens stretching from the beach to a landscaped jungle hillside (111 Moo 6, Hat Khlong Nin; from £125).

The Library, by Chaweng beach on Ko Samui, is decorated in sparkling white – except for the dramatic red-tiled pool. The resort is a study in pared-back and contemplative design, with iMacs in every room (14/1 Moo 2; from £270).

Bangkok’s Suvarnabhumi Airport is served by BA and Thai Airways from Heathrow (from £820). Air-hopping around the country remains an affordable option, with operators including Bangkok Airways and Air Asia. Most routes originate from Bangkok (Ko Samui from £140). Ko Samui is the only island in this guide you can fly to. Ferries serve the other islands from mainland transport hubs, including Trat, Surat Thani, Chumphon, Krabi and Trang, often with a dedicated bus service to the relevant pier. It’s best to check your guidebook for specific details and providers.

The article 'Mini guide to Thailand’s islands' was published in partnership with Lonely Planet Traveller.