The Criminal Court sentenced red-shirt leader Jatuporn Prompan to two years in jail over charges of insulting former premier Abhisit Vejjajiva in a speech five years ago.
The court said that Jatuporn's comments on stage against Abhisit on October 11, 2010, at Victory Monument and on October 17 of the same year were untrue and could therefore be considered defamatory.
The court has also ordered Jatuporn to publish the court's sentence in Thaipost, Matichon and Daily News newspapers for seven days.
Jatuporn was granted bail with a Bt200,000 guarantee and his lawyer said the case would be taken to the Appeals Court.