The Supreme Court's Criminal Division for Holders of Political Positions has acquitted former protest leader Suthep Thaugsuban of corruption in projects to construct police stations and living quarters while he was deputy prime minister more than a decade ago.
The court also acquitted five co-defendants in the case -- three senior police officers, a construction company and its managing director.
The projects were approved during the administration of then prime minister Abhisit Vejjajiva, when Mr Suthep was a deputy prime minister.
The National Anti-Corruption Commission (NACC) filed the case with the court, alleging malfeasance and price collusion in government projects from June 2009 to April 2013.
One project relates to the construction of 396 police stations, worth 5.84 billion baht, which was endorsed by Mr Abhisit's cabinet.
Many of the police stations were left unfinished when the contractor, which was managing a number of construction sites at the same time, allegedly dumped the project.
The NACC also found grounds for allegations relating to the building of 163 blocks of police flats which had been proposed along with the police station project. The same firm was also contracted to build the flats which also suffered delays.
Mr Suthep and Pol Gen Pateep Tanprasert, former acting national police chief, were accused of wrongfully combining all the regional construction contracts into one.
The contract was then awarded at an unusually low price to a single contractor, PCC Development & Construction Co.
Pol Maj Gen Satja Kochahiran and Pol Lt Col Suriya Jangsuwan, who were on the bidding committee, were accused of failing to verify the quote.
Wisanu Wisetsing, the PCC Development & Construction managing director, was accused of tendering a quote that was too low and the company of failing to finish the work.
The court found that the Royal Thai Police had the authority to decide how it would award the construction contract and Mr Suthep could not be held responsible for any malfeasance.
The court also found that Pol Gen Pateep handled the project in compliance with regulations, and there was no evidence that Pol Maj Gen Satja and Pol Lt Col Suriya had any vested interest.
The company and its managing director were thus considered innocent, and the low quotation was the company's own decision and did not cause any damage to the state.
Speaking after leaving court on Tuesday, Mr Suthep said he was glad to have cleared his name.
"I co-founded the Action Coalition for Thailand (ACT) Party which has five MPs and one cabinet minister in the government. I have been under attack [over the case] for a decade. But from now on, I have great morale to carry on.
"I will not stand in an election, but will help groom decent politicians to work for the people. I will do anything I can to help. I will keep the promise I made when leading the protest that I will not return to politics," said Mr Suthep, former leader of the now-defunct People's Democratic Reform Committee.
Asked if the ACT will support Gen Prayut Chan-o-cha carrying on as prime minister, Mr Suthep said it remains to be seen how the Constitutional Court rules on his eight-year tenure as premier on Sept 30.