A leading Thai "Red Shirt" leader was Tuesday cleared of slander over claims that he accused the former premier of sitting incorrectly during an audience with the king, his lawyer said.
Jatuporn Prompan, who was last year found guilty of slandering former Prime Minister Abhisit Vejjajiva in 2009, had his conviction overturned by the Court of Appeal in Bangkok.
"The verdict said Jatuporn honestly expressed his opinion and that the general public did not have to believe him," his lawyer Winyat Chatmontree told AFP.
He added that the former MP had made an innocent mistake in his criticism of Abhisit because he "has no idea of royal protocol".
The Red Shirts are a group which supports the country's deposed former Prime Minister Thaksin Shinawatra.
In the original case, the Thai Criminal Court heard that the firebrand activist accused the then-Thai leader Abhisit of sitting on a chair of an equal height to one being used by King Bhumibol Adulyadej.
In Thailand, where it is customary to remain at a lower level than the monarch, such a move could be seen as discourteous.
In court Abhisit successfully argued that since the chair had been provided by the royal household, his use of it could not be seen as a mark of disrespect.
The monarchy is a highly sensitive topic in politically turbulent Thailand, where the 85-year-old king is revered as a demi-god by many Thais.
Strict lese majeste laws prohibit any insult to the monarch and carry potential prison terms of up to 15 years per count.
Jatuporn, who is facing a series of court cases including one alleging terrorism over massive 2010 Red Shirt protests that ended in bloodshed, was sentenced to six months in prison, suspended for two years, in the original slander case in July 2012.
"I thank the judges, who gave me mercy," he told AFP, declining to comment further of the details of the appeal hearing.
Jatuporn was formerly an opposition MP for the now-ruling Puea Thai party but was stripped of his parliamentary seat in May 2012.