Thailand will explore legal channels for asking China to extradite former leader Thaksin Shinawatra, convicted of graft and on the run overseas, Prime Minister Abhisit Vejjajiva said on Thursday.

Abhisit's statement was in response to Thaksin's plan to deliver a luncheon speech titled "Financial Crisis, Political Uncertainty: Lessons from Thailand" at the Foreign Correspondents Club in Hong Kong on Monday.

The club said Thaksin would address its members in his capacity as founding chairman of the Building a Better Future Foundation.

"We will look into any possible legal channel. If viable, responsible police and prosecutor agencies will handle it," Abhisit told reporters.

"It is within the personal rights of the former prime minister to use any venue for making his speech. But the Thai government will clarify and rebut any derogatory statements directed at the country," he said. Thaksin, ousted in a bloodless coup in 2006, was convicted by a Thai court last year for breaking conflict of interest laws while in office. He said the verdict against him was politically motivated.

Thaksin has remained a highly popular figure among rural Thais who have benefited from his past populist economic policies, some of which have been adopted by Oxford-educated Abhisit who came to office after a snap election in December.

Thaksin's aides say the former telecom billionaire turned politician decided against returning to Thailand on concern for his safety.

The former leader, in power 2001-2006, has inflamed political passions in recent months by addressing big public rallies of his largely rural supporters via teleconference.

Thousands of Thaksin's red-shirted supporters have launched a street campaign against Abhisit since Tuesday by marching on the seat of government in Bangkok.

Their protest is aimed at embarrassing Abhisit on the eve of a summit of 10 Southeast Asian leaders at the seaside resort of Hua Hin southwest of Bangkok this weekend.

Reuters