Sirichoke Sopha was found to have defamed former transport minister Pongsak Ruktapongpisal in October last year after asserting without justification that Pongsak's involvement in the Thailand Plaza deal in New York caused losses of Bt240 million, the court said.

Pongsak sued Sirichoke, citing an interview he gave with the media following a debate in the House, which provided immunity for remarks made in Parliament.

In its sentencing, the court said Sirichoke faced a penalty of three months in jail. But his libel happened in connection with the House debate and was in line with the public interest, hence there were grounds for leniency, it said in waiving the jail term.

Sirichoke was ordered to publish a summary of the verdict in Matichon newspaper.

The court dismissed an auxiliary charge against Matichon for publishing the interview, saying the newspaper adhered to its journalistic duty to report what was in the public interest. Lawyers for the defence and the plaintiff both said they would appeal the ruling.

Sirichoke's lawyer Thanuwat Phumee said his client would seek to be acquitted at the appellate review.

Plaintiff lawyer Bancha Parameekanaporn said his client wanted to overturn the acquittal verdict for Matichon.