
Suthep submitted the request to House Speaker Chai Chidchob, who will need a royal endorsement before reconvening parliament to vote on new PM and set up a new government.
Suthep claimed his party has secured enough support from the "Friends of Newin" breakaway faction from the Pheu Thai and its former allies the Chart Thai, Matchiamathipataya, Puea Paendin and Ruam Jai Thai Chart Pattana parties to form a new coalition government.
He said the new alliance provides a Democrat-led government about 260 seats in the 438-seat Lower House of Parliament, with the Democrats holding 165 seats. The Puea Thai party, a reincarnation of the now defunct People Power Party, claims to have at least 219 seats.
If the Democrats' alliance does not fall apart before the reconvening of Parliament some time this week, Democrat leader Aphisit is likely to become Thailand's next prime minister.
Democrat Party leader Abhisit Vejjajiva said the Democrat Party had 30 votes of support from the Newin's Friends group and that would enable the party to muster the majority control of 260 votes.
He was speaking after Democrat Party secretary-general Suthep Thaugsuban on Monday submitted a motion to House Speaker Chai Chidchob, requesting him issue a royal decree to convene an extraordinary session of Parliament to elect a new Prime Minister.
Suthep turned up at Parliament with leading members of the Democrat and representatives of other political parties at 10 am..
Suthep said the 30 MPs from the Friends of Newin group had yet to sign their names in the motin because they fear being threatened and pressured.