Acting on Thaksin's behalf, lawyer Chalermkiart Saikaew filed a plaintiff writ charging the daily for defamation relating to its front-page report on March 20.

"The Nation's headline 'Thaksin loses royal duty' is false," Chalermkiart said, talking to reporters after lodging the suit at the Criminal Court. The litigation should not be seen as media harassment but an attempt to protect Thaksin's reputation, he said.

The Privy Council did not convene a meeting to replace Thaksin as chairman of the organising panel to commemorate HM the King's 60th accession to the throne, he said.

Defendants include Nation Multimedia Group, MMG News and Pana Janviroj, president of The Nation.

The plaintiff seeks to penalise the defendants by asking them to publish the guilty verdict for 15 days in nine newspapers. The court will rule on June 19 whether the case merits a judicial review.

In the second case, Thaksin sued Sondhi for his alleged malicious comments made at rallies held at different locations last month.

On March 3, Sondhi spread false information that Thaksin had spent Bt300 million to win the loyalty of cronies, and gave away money to secure his popularity, the writ states.

Ten days later, Sondhi remarked that Thailand was the only country in the world to be under the leadership of a crazy man, the writ said.

Thaksin asked the Criminal Court to order Sondhi to publish a guilty verdict in his Phujadkarn newspaper for nine days. The court will rule on the case on June 5.

In another development, Sondhi filed a libel lawsuit against Thai Rak Thai executive Newin Chidchob.

Representing Sondhi, lawyer Suwat Apaisak submitted the plaintiff writ accusing Newin of giving an interview on March 24 portraying his client as committing lese majeste.

Suwat said Newin had timed his comments to defame Sondhi as well as try to influence the legal proceedings relating to the lese majeste charge lodged against him.

The court is to decide on June 19 whether the case merits a review.