Defecting MPs could threaten the survival of the Abhisit government when the 2011 budget bill faces a vote for final approval in Parliament later this year.
If the crucial bill is not passed, the government will be dead.
Given that the government's majority in Parliament is now slim following the latest Cabinet reshuffle, Abhisit will need virtually every vote to get the budget approved.
Some Democrat Party MPs and other junior coalition party MPs from the North and Eastern provinces were reportedly upset by the Cabinet reshuffle because they did not get ministerial posts. Democrat MPs from the North and Northeast were shocked to see their leader, Phaitoon Kaewthong, lose the Labour portfolio.
Meantime, Pheu Thai Party claims some government MPs are seeking to join the Opposition.
There was also speculation that ex-premier Thaksin Shinawatra would topple the government by "buying" government MPs to vote down the budget bill.
Pheu Thai deputy spokesman Jirayu Huangsab claimed the government was struggling to ensure it had enough votes to pass the budget bill.
PM Abhisit would not dare to take drastic action against ministers from the Bhum Jai Thai Party, a key partner of the coalition government, if they were accused of corruption, he claimed. "There will be a surprise in the final House debate on the 2011 budget,'' Jirayu said.
Newly appointed ICT Minister Juti Krairerk from the Democrat Party said Thaksin could "buy" MPs to topple the government.
Key members of the opposition Pheu Thai Party had entered into talks with Puea Pandin Party MPs recently ousted from the coalition including Puea Pandin Party MPs under the control of Pinit Jarusombat, Pairote Suwunchwee and Preecha Laohapongchana to discuss an alliance.
These MPs were ousted after they cast votes in the censure debate against Interior Minister Chavarat Charnvirakul and Transport Minister Sophon Saram of the Bhum Jai Thai Party.
Prime Minister Abhisit, however, said he was not worried by the possibility of MPs defecting at this stage.
Finance Minister Korn Chatikavanij added that every government party would eventually tow the line even if some of their MPs were disappointed by the latest Cabinet reshuffle.