Activist Srisuwan Janya has filed a petition against four government MPs with the National Anti-Corruption Commission (NACC) in connection with alleged vote fraud in the budget bill.
The four MPs are Chalong Therdwirapong, Somboon Zarum and Natee Ratchakitprakan, all from the Bhumjaithai Party, and Parim Poolcharoen, from the ruling Palang Pracharath Party.
The bill's deliberation and its third reading vote took place from Jan 8-11.
Mr Chalong admitted he was at a funeral in Phatthalung on Jan 10 when his vote was cast. He said he had left his electronic voting card behind in a House voting machine.
Nipit Intarasombat, the former Democrat Party MP who exposed the voting irregularity, also claimed that Ms Natee also voted for the bill without being present in the House.
He showed an air ticket and a picture of Ms Natee passing through an immigration checkpoint at Suvarnabhumi airport to board a plane heading to China at the time her vote for the budget bill was logged.
It was reported Mr Somboon and Ms Parim were seen inserting the voting cards of other MPs into the slots inside the chamber during the bill's deliberation. It was unclear if the cards belonged to Mr Chalong or Ms Natee.
On Monday, Mr Srisuwan accused the four MPs of violating Section 185 of the constitution by resorting to interference for personal gain or others' vested interested. They could also be guilty of an ethical violation and breach of NACC rules, he said.
If the four are found guilty, they stand to lose their MP status, according to the activist.
The alleged voting fraud has ignited a legal question over the validity of the budget bill which has now cleared the Senate too. The fate of the bill is in doubt after the House petitioned the Constitutional Court which will decide tomorrow whether to accept the case for examination. If accepted, the bill will be put on hold pending a ruling.