Former Thai prime minister Abhisit Vejjajiva has been indicted on charges of murder in connection with a military crackdown against mass protests in the capital Bangkok three years ago.
More than 90 people died and nearly 2000 were wounded in 2010 when security forces fired live rounds at demonstrators supporting former president Thaksin Shinawatra.
The BBC reports Mr Abhisit, who leads the opposition Democrat Party, denied the charges and was granted bail.
Meanwhile, protests against current Prime Minister Yingluck Shinawatra continued outside Government House on Thursday. Power to the premises was also reportedly cut.
Protest leader Suthep Thaugsuban, who was Mr Abhisit's deputy in 2010, also faces charges but has asked the court to postpone his hearing.
Mr Abhisit and Mr Suthep were in power when supporters of Mr Thaksin occupied parts of Bangkok for two months. They authorised the army to clear the protesters.
Anti-government protesters want Ms Yingluck to resign and for her government to be replaced with an unelected People's Council.
They say that Mr Thaksin, who is also Ms Yingluck's brother, controls the ruling Pheu Thai party.
The BBC reports Mr Abhisit and other Democrat Party MPs resigned from parliament on Sunday so that they could join the protesters.
On Monday, Ms Yingluck dissolved parliament and announced general elections for 2 February, as 150,000 protesters surrounded Government House.
However, she has refused to resign before the elections.
The Pheu Thai party has a majority in parliament, and draws significant support from Thailand's rural areas. The party is seen as well-placed to win February's election.