Thailand has banned protests and the publication of sensitive news in the face of escalating protests that have targeted King Maha Vajiralongkorn as well as Prime Minister Prayuth Chan'ocha, a former junta leader.
Within 30 minutes of an emergency decree taking effect at 4 am on Tursday, riot police advanced on protesters camped outside Prayuth's office to demand his removal and a new constitution.
Police said they arrested about 20 people who refused to co-operate, including two of the protest leaders who have been most vocal in criticing the monarchy.
To justify emergency measures including a ban on gatherings of five or more people, the government cited the obstruction of a royal motorcade, growing disorder, economic damage and the risk of spreading coronavirus.
"It is extremely necessary to introduce an urgent measure to end this situation effectively and promptly to maintain peace and order," the decree said.
The latest demonstration brought out tens of thousands of protesters on Wednesday.
They marched to Government House and vowed to stay put until Prayuth left. Most left overnight. The few who tried to resist the police advance behind makeshift barricades were quickly cleared.
"We haven't been able to restore a true democracy yet," said 54-year-old Sun Pathong, a veteran of a decade of anti-estbalishment protests and counter protests before Prayuth took power in a 2014 coup.
"I'll be back. We have to continue the fight even if we risk our lives."
Student leader Panusaya "Rung" Sithijirawattanakul said protesters would go ahead with a protest planned for 4 pm but police spokesman Kissana Phathanacharoen told reporters the planned protest was banned.
The decree also bans publishing news or online information that "could create fear" or "affect national security".
Police said they had arrested protest leaders Parit "Penguin" Chirawat and rights lawyer Arnon Nampa.
Thai Lawyers for Human Rights said its earlier statement Panupong Jadnok was also arrested was incorrect. Twenty other protesters are still being held after a demonstration on Tuesday.
The protest movement aims to remove Prayuth, saying he manipulated an election last year to keep power. He says the election was fair.