Mr Chidchai's mastery of security issues led Mr Thaksin to appoint him as his top deputy prime minister last month, after the government came under fire from demonstrators demanding Mr Thaksin's resignation for alleged corruption and abuse of power.

Mr Chidchai was first appointed interior minister and a deputy prime minister in March last year. But because his mandate to handle the problems in the south kept him too busy to oversee the huge Interior Ministry, he was shifted to justice minister in August.

He led Mr Thaksin's war on drugs, in which the government was accused by human rights activists of carrying out the extrajudicial killing of suspected traffickers.

Mr Chidchai is considered a safe pair of hands given the current tensions. However, as the constitution stands, he cannot take the premiership because he is not an elected member of parliament.

A new government can only be formed once parliament opens. In theory, that government selects a prime minister, who must then be endorsed by the rest of parliament.

Among the contenders is Somkid Jatusripitak, now serving as deputy prime minister and minister of commerce. Holding a doctorate in business management and marketing from Northwestern University in the US, Mr Somkid, 52, has been at the core of Mr Thaksin's economic policies since Thai Rak Thai was founded in 1992.

After Mr Thaksin's televised resignation on Tuesday, he turned to hug Mr Somkid, who has said he would be reluctant to take the job.

Mr Somkid has constantly talked up Thailand's growth potential, defended easy credit policies and sought to engage the region with controversial free-trade deals. China has been a focus of his work, with Mr Somkid staging missions from Kunming to Beijing.

'We recall and remain truly appreciative of China's positive role during the Asian financial crisis of 1997, just as we, today, admire China's positive actions in the international trade and financial arena,' he said on a recent trip.

His appointment would generate support within business and trade circles, but insiders believe he would have to work hard to build local popularity.

Insiders are also watching outgoing parliamentary Speaker Bhokin Bhalakula.

The 54-year-old is reportedly extremely close to Mr Thaksin, having taken on some of his most sensitive tasks as interior minister, including tsunami recovery efforts.

But his closeness to Mr Thaksin could cause him problems should any new cabinet seek to distance itself from the billionaire.

Surakiart Sathirathai is another deputy prime minister and Thai Rak Thai founder being eyed for the post. Mr Surakiart boasts both academic and private-sector experience in the wake of the Thai collapse in the Asian economic crisis.

Thailand's youngest foreign minister, the 47-year-old was recently elevated to deputy prime minister in part to promote his campaign to replace Kofi Annan as secretary-general of the United Nations later this year - a drive that may put him out of contention.

Long-serving parliamentarian Sudarat Keyuraphan has ruled herself out of contention, but is still surfacing as a possible contender.

Mrs Sudarat served in ministerial-level posts through the mid-1990s, acting as a leader of the Palang Dharma Party, which introduced Mr Thaksin to politics.

She is now the minister of agriculture - an area related to Mr Thaksin's key support base in the countryside.