Anti-government PAD says it will oppose efforts to see Samak returned to power.
Five parties in the ruling coalition have not endorsed Samak’s re-nomination, leaving the country mired in a political deadlock that has raised fears of instability and economic chaos.
Last week Samak imposed a state of emergency in the capital following violent clashes between his supporters and anti-government protesters who have been occupying the grounds of the prime minister’s office since late August.
Protesters led by the People’s Alliance for Democracy (PAD) – a mixture of royalists, businessmen and union activists – have said they will stay on until an acceptable leader is found.
Meanwhile General Anupong Paochinda, the country’s army chief, said he has already asked the interim leadership to end emergency rule in Bangkok.
“Keeping it in place will damage the country’s economy,” he said.
Anupong also threw his support behind an opposition proposal to form a national unity government that would include all political parties.
“A national unity government is the best way to end the ongoing political crisis,” he added.
The comments are likely to fuel speculation of a coup despite military officials repeatedly denying any intervention to end the political stalemate.
Thailand has seen more than a dozen coups since it became a constitutional monarchy in 1932, the most recent in 2006 when Thaksin was removed from office.