Thai Prime Minister Thaksin Shinawatra on Monday sued an anti-government protest leader and 11 others for defamation and demanded $26 million in damages, his lawyer said.
The civil lawsuit joins a string of defamation cases filed by Thaksin. Last month the premier filed another defamation suit against Thailand's main Opposition Democrat Party and its leaders for accusing him of tax evasion.
In the latest suit, Thaksin and his ruling Thai Rak Thai party sued media tycoon and anti-Thaksin activist Sondhi Limthongkul and 11 others for defamation and demanded one billion baht ($26 million) in damages.
Sondhi and the critics allegedly said during a televised seminar in May that Thaksin and his party members were trying to undermine the country's revered monarchy, lawyer Thana Benjathikul said.
Along with the critics, Thaksin sued the state-run Communications Authority of Thailand for renting Sondhi satellite TV equipment.
Sondhi, once one of Thaksin's staunchest supporters, has become the leader of the People's Alliance for Democracy (PAD), which led street protests against him earlier this year.
The protests broke out after Thaksin's family earned $1.9 billion in a tax-free stock sale in January, with critics accusing the premier of using his political office to enrich his business empire.