The Criminal Court has found Watana Muangsook, a prominent Pheu Thai Party figure, not guilty in a case related to remarks he made about the disappearance of the plaque marking the Siamese Revolution of 1932 from the Royal Plaza.
The court said on Friday that comments Mr Watana posted on his Facebook page were opinions that could not be deemed a computer crime. They posed no threat to security, the court added.
The court said his messages could be considered in the context of academic freedom and his criticism of authorities did not reflect ill intent.
Public prosecutors charged the outspoken politician with violating the Computer Crimes Act and Section 116 of the Criminal Code on instigating chaos, for comments he made on social media between April 17 and May 30 last year.
His comments were made after the Khana Ratsadon memorial plaque commemorating the 1932 Siamese Revolution at the Royal Plaza was mysteriously removed. Despite inquiries made by Bangkok Metropolitan Authority officials, no trace of it has been found.
A new plaque with a new message not related to the revolution was installed at the same spot.
Mr Watana had pleaded not guilty.
The Computer Crimes Act has been applied very broadly by the current military government to target its critics, with the result that free speech has been limited.
It is also not uncommon for those charged with criminal defamation to also be charged with computer crime if their comments appeared online.