Thai police arrested a key leader of a month-long protest inside Bangkok's Government House compound on Sunday, but the detained anti-government figure urged his supporters not to quit.
In a short letter read out on the People's Alliance for Democracy's (PAD) television channel, Chamlong Srimuang likened the movement's bid to overthrow the elected government to a sacred national duty.
"We are gathering to repay the country and to make merit for Thailand," Chamlong, an ascetic Buddhist and retired general who has been a driving force behind the PAD for three years, said in the letter.
"It's the duty of all Thais. No matter what happens, remember that the duty of Thais is to serve the country, religion and King. We are all born with that duty, of repaying what we owe to the country," he said.
Chamlong was arrested after leaving the prime minister's official compound, where he and thousands of anti-government protesters have been barricaded since late August, to go and vote in the capital's mayoral elections.
His pre-written letter raised speculation he had intended to be arrested.
A court issued arrest warrants for Chamlong and eight other PAD figureheads on August 27th, the day after thousands of protesters broke into government ministries and a state television station before overrunning Government House.
The nine were accused of inciting unrest and trying to overthrow the government, charges that amount to treason and can carry the death penalty.
However, police were unable to execute the warrants since the nine refused to leave the Government House compound, where hundreds of PAD protesters have barricaded themselves in.
The first of the nine to be arrested, Chaiwat Sinsuwong, was picked up at his home on Friday after leaving the compound.
There was no immediate comment from the police about Chamlong's arrest.
New Prime Minister Somchai Wongsawat has tried to open negotiations with the PAD, who accuse him of being a political proxy for his brother-in-law, Thaksin Shinawatra, who was removed in a 2006 military coup.
However, no real talks have started and there has been little prospect of the PAD, which claims to be acting in the name of revered King Bhumibol Adulyadej, leaving Government House any time soon.
After a meeting with the opposition leader and parliamentary leaders on Friday, Somchai said all sides had agreed on the idea of reforming the constitution drawn up by the army after the coup as a possible way out of the current stalemate.