The terrorism trial of leaders of Thailand's 2010 "Red Shirt" protests began on Friday, a day after a former premier was charged over his role in the bloody street battles which left scores dead in Bangkok.
The 24 accused, who include five current lawmakers, could in theory face the death penalty in the case, which was delayed again on Thursday because of the absence of key witnesses.
All but one defendant was present at Bangkok Criminal Court on Friday, according to an AFP reporter.
About 90 people were killed and nearly 1,900 wounded in a series of street clashes between demonstrators and security forces, which culminated in a military crackdown in May 2010. Two foreign journalists were among those killed.
Tens of thousands of anti-government demonstrators occupied parts of central Bangkok for weeks, erecting barricades of sharpened bamboo, before the army ended the standoff.
Proceedings against the Red Shirt leaders will likely drag on for years, with counsel on both sides calling several hundred witness -- although the court is likely to trim the list to around 200 in total.
Hearings can only be held when parliament is not in session since sitting lawmakers have immunity, meaning next Thursday's trial day will be the last until April next year.
The Red Shirt leaders, most of whom surrendered to police after the government sent in armoured vehicles and troops firing live rounds, pleaded not guilty in 2010 and have vowed to prove their innocence.
Key Red Shirt leader Jatuporn Prompan on Thursday told reporters at the court that the group would "fight the case to the end".
"But people of every political group should be granted an amnesty," he said.
Abhisit Vejjajiva, who was prime minister during the anti-government rallies, and his then-deputy Suthep Thaugsuban were charged with murder on Thursday over the death of a taxi driver shot by soldiers during the violence.
They are the first officials to face court over Thailand's worst political violence in decades. The pair have denied the allegation.
Although Abhisit is unlikely to ever face jail the trial is a breakthrough for Thailand's justice system, according to Thitinan Pongsudhirak of Chulalongkorn University, and signals a challenge to the culture of impunity which pervades the politically polarised kingdom.
"This is the first time government leaders have been held accountable for the death of protesters... future government leaders will think twice before using force against demonstrators," he added.
Thailand has been racked by sometimes explosive political divisions since a 2006 coup deposed then-premier Thaksin Shinawatra.
The Red Shirts -- mostly supporters of the ousted premier -- were demanding immediate elections in their 2010 protest.
They accused Abhisit's government of being undemocratic because it took office in 2008 through a parliamentary vote after a court stripped Thaksin's allies of power.
Polls in 2011 brought Thaksin's Red Shirt-backed Puea Thai party to power with his sister Yingluck as premier, sweeping Abhisit into opposition.