By Chalathip Thirasoonthrakul
BANGKOK (Reuters) - Thailand's opposition Democrat Party called on Monday for an urgent parliamentary session to select a new prime minister, claiming it had won over enough lawmakers to form a coalition government.
In a petition to the speaker of parliament, the Democrats said a vote to succeed the administration sacked last week by the courts could be held sometime between December 12 and December 26.
"After talking to other parties, they will cooperate with us to form a new government, led by the Democrat Party," Abhisit Vejjajiva, the party's 44-year-old Oxford-educated leader and candidate for prime minister, told reporters.
House Speaker Chai Chidchob said he would set a date after checking the signatures on the petition, which also needs royal endorsement before the session can be convened.
The outcome of this latest skirmish in Thailand's protracted political crisis, which escalated when anti-government protesters seized Bangkok's main airports recently, is far from certain.
The Democrats claim their party and its new allies have secured 260 votes in the 480-seat parliament, enough to form a new government.
However, the party containing allies of ousted Thai leader Thaksin Shinawatra also claimed on Sunday it had enough support to cobble together a coalition.
"Our former coalition partners will join us. We now have enough votes," said Kanawat Wasinsungworn, deputy leader of Puea Thai, the replacement for the People Power Party (PPP) banned by the courts last week.
Normally, Thailand's parliament has 480 seats but that number has been thrown into confusion by last week's court ruling, which saw dozens of MPs from the PPP and two other parties barred from politics for five years.
It is unclear when by-elections will be held to fill the empty seats, or whether there might have to be another general election -- the fourth in as many years.
Immediately after last Tuesday's court ruling, the interim PPP cabinet said the vote should take place on December 8 and 9, although King Bhumibol Adulyadej did not grant his approval for a special session.
Since then, the influential 81-year-old monarch has been taken ill, missing his traditional birthday eve address to the nation on Thursday. The palace has said his condition is improving.
The anti-Thaksin People's Alliance for Democracy (PAD) ended its blockade of the airports on Wednesday, the day after the court ruling, but it has vowed to take to the streets again if what it terms "Thaksin nominees" get close to power again.
Solid support among the rural and urban poor for Thaksin, who was removed in a 2006 coup and is now in exile with a corruption conviction to his name, is likely to ensure a broadly sympathetic party wins any election.
Tensions look set to rise again this weekend when Thaksin is due to hold a "phone-in" to a rally of his supporters in Bangkok.
"On December 13, Mr. Thaksin will tell us everything about how Thailand's democracy has been interfered with," Jatuporn Prompan, a PPP MP and radio show host, told reporters.
"He will tell us who did what during the intervention and how they are doing it. He will also tell us about his plan to fight back," he said.
Thailand has been in crisis for three years, with Bangkok's royal and military elites pitted against Thaksin and his allies in the PPP, which won an election a year ago to end 15 months of army-backed government after the coup.
(Writing by Darren Schuettler; Editing by Alan Raybould and Bill Tarrant)