BANGKOK: Thailand's outgoing Prime Minister Abhisit Vejjajiva was re-elected on Saturday as leader of the now-opposition Democrat Party, despite fronting their crushing defeat in July's general election.

A day after his rival Yingluck Shinawatra of the Puea Thai party won parliamentary approval to become the new Thai premier, the pro-establishment Democrats re-selected Abhisit to lead them after he ran unopposed for the job.

“He's the most suitable person,” veteran party member Marut Bunnag told a party meeting in Bangkok, observed by AFP, before Abhisit won 96 per cent of the votes.

Abhisit, who became prime minister in December 2008, had resigned last month as Democrat leader after his party clinched just 159 seats against Puea Thai's 265 in the July 3 election. He first became party leader in 2005.

New premier Yingluck is due to receive royal endorsement to formalise her position on Monday afternoon, the house speaker said Saturday.

The sister of fugitive former leader Thaksin Shinawatra, who was toppled by a military coup in 2006, she faces the tough challenge of bringing unity to the politically volatile kingdom.