Thai police have arrested nine people in a sweep targeting activists involved in recent anti-government protests.
Among the nine was lawyer Anon Nampa, who was charged over a Harry Potter-themed protest in Bangkok at which he called for reform of the monarchy.
Thailand's monarchy has long been shielded from criticism under strict lese-majeste and other laws.
But in recent weeks, students and other activists have taken to the streets to call for reforms of the institution.
Mr Anon, 36, was the first to openly break the taboo at the protest, which took place earlier this month.
Among the others detained after Mr Anon were activists Baramee Chairat, Suwanna Tarnlek and Korakot Saengyenpanm, and two popular rappers: Dechatorn Bamroongmuang, from the group Rap for Democracy; and Thanayut Na Ayutthaya, better known as Elevenfinger, both of whom performed on stage at a July protest at Bangkok's Democracy Monument.
The activists were charged with sedition and could face prison sentences of up to seven years. All were later released on bail. Activists said they had seen a police list of 20 more facing possible arrest in the near future.
The protesters are demanding dissolution of the government headed by Prime Minister Prayuth Chan-ocha, a former army chief who seized power in a 2014 military coup and returned as the country's civilian premier after a controversial election last year.
Extraordinary shift to monarchy
The anti-government rallies took an unprecedented turn earlier this month when they began to include calls for reform to the monarchy.
Thais are taught to respect, revere and love the monarchy, but also to fear the consequences of speaking about it.
Insulting the monarchy in Thailand can mean up to 15 years in jail under the kingdom's lese-majeste law.
The use of this legislation has slowed in recent years as Thai King Vajiralongkorn has let it be known he no longer wants it so widely used. But observers say the government has used other legal routes to target dissent, including the sedition law.
Mr Anon's arrest on Wednesday saw him charged with sedition for a second time this month. He was earlier arrested over the July rally with another activist, Panupong Jaadnok.
This latest arrest is over the Harry Potter-themed protest that took place in Bangkok on 3 August, where Mr Anon had stressed that he wanted to reform, not overthrow, the constitutional monarchy.
He focused in particular on the huge assets of the Crown Property Bureau which, under the late King Bhumibol, had been notionally held in trust for the benefit of the Thai people, but have now been declared the personal property of the king, making him by far the wealthiest person in Thailand.
Mr Anon also questioned King Vajiralongkorn's decision to take personal command of all military units based in Bangkok, something he believes cannot be compatible with a democratic, constitutional monarchy.
"It had to be done," he said of his call for accountability.
"That's why I chose to speak candidly, to honour my own integrity, the integrity of the audience, and out of respect for the monarchy. Because if we don't speak frankly about it, then we will never understand it."
'Crackdown on pro-democracy activists'
His comments were nothing short of extraordinary in a country where few dare to openly discuss the institution. In recent years, critics of Thailand's monarchy who have fled to neighbouring countries have been abducted and murdered.
Thai police are cracking down on the student-led movement that has given rise to the country's biggest rallies since the coup six years ago.
Protesters seek the resignation of the military-backed government, an end to the harassment of its critics, a new constitution and fresh elections.
"The Thai government's repeated promises to listen to dissenting voices have proven meaningless as the crackdown on pro-democracy activists continues unabated," said Brad Adams, Asia director at Human Rights Watch, calling for authorities to drop the charges and release all the activists.
Ming Yu Hah, Amnesty International's Deputy Regional Director for Campaigns, accused the Thai authorities of "weaponising the law to silence people who peacefully criticise the government".
"The authorities must drop these bogus charges against peaceful protesters," he said. "Freedom of expression and freedom of peaceful assembly are human rights, even if the government disagrees with the criticisms being levelled at them."