The Pathumwan District Court has acquitted an anti-coup protester on grounds he was investigated by unauthorised officers.
The court on Thursday threw out the case against Apichart Pongsawath after ruling that the Crime Suppression Division had no authority to handle the case as it was under the jurisdiction of Pathumwan police station.
Sgt Maj Apichart was indicted by state prosecutors on April 28 for defying a political gathering ban ordered by the National Council for Peace and Order and inciting trouble on May 23 the previous year.
Sgt Maj Apichart, who works for the Law Reform Committee, was arrested by soldiers on that date while displaying an anti-coup message reading: "Do not recognise the barbarian forces" with about 500 others in front of the Bangkok Art and Culture Centre in Pathumwan district, according to the court document.
The protest came one day after then-army chief Gen Prayut Chan-o-cha seized power from the government led by Yingluck Shinawatra.
He was taken to the 2nd Cavalry Division King's Guard for detention for one night before soldiers handed him to the CSD for further interrogation.
Sgt Maj Apichart, 26, who is pursuing a master's degree at Thammasat University, denied the charges on grounds that people had the right to express opinions against a coup and that the gathering on May 23 was peaceful.
The court then decided not to continue the case because wrong interrogators were used. He said after the verdict that he will not counter-sue the authorities handling the case.
"The fact that the court acquitted me today should be a testimony that another 30 coup opponents who were previously arrested, charged, confessed and convicted should have also been freed due to unauthorised investigations as well," Sgt Maj Apichart said.
The prosecutors have 30 days to decide whether to take the case to the Appeal Court.
A prosecutor said the full text of the written verdict would be studied before a decision is made.