Two red shirts were acquitted yesterday of setting fire to the CentralWorld shopping complex at the end of anti-government protests in May 2010.
The Southern Bangkok Criminal Court freed Saichol Paebua and Pinij Channarong, citing a lack of witnesses and evidence.
Saichol and Mr Pinij were among four defendants accused of setting fire to the shopping complex during the 2010 red-shirt political violence.
The other two suspects were tried separately in the Central Juvenile and Family Court and were acquitted late last year, also because of a lack of evidence.
The court ordered the release of Saichol and Mr Pinij yesterday, giving them the benefit of the doubt after prosecutors failed to produce the policemen who arrested Mr Pinij in the CentralWorld carpark on the evening of 19 May 2010.
The court also said CentralWorld security and fire-fighters who testified could not confirm they saw Mr Pinij set fire to the shopping centre.
Saichol, who was arrested a month later at Sanam Luang, was also freed because state witnesses could not provide firm evidence that he had set fire to the shopping complex.
The court sentenced him to one year in prison for violating the emergency decree that was in place during the violence. However, the sentence was commuted to nine months because he was cooperative during the investigation.
He was then immediately released for time already served while on remand.
Saichol, from Chai Nat, burst into tears while Mr Pinij, from Chaiyaphum, beamed broadly after hearing the court's ruling.
Noopit Channarong, 46, Mr Pinij's mother, said she was relieved and would like to thank everyone who helped in her son's defence.
"He is a gentle person, and not a belligerent or gung-ho type. Our family was convinced all along he was innocent," said Ms Noopit, who travelled with her husband from Chaiyaphum province to pick up their son from the prison.