A charter amendment plan seeking to strip the Senate of its power to take part in electing a prime minister is due to go before a joint sitting for debate today, according to the opposition whip.
However, both the government and the opposition agreed achieving success will be an uphill battle as the Senate is unlikely to vote to remove its own power.
Sutin Klungsang, chief opposition whip, said the joint sitting is taking place today and tomorrow, with the charter amendment plan topping the agenda.
Specifically, the charter amendment plan calls for a change to Section 272 of the constitution, which allows the Senate to join MPs in electing a prime minister.
The amendment is being pursued via five draft bills, one of which is sponsored by Somchai Srisutthiyakorn, Seri Ruam Thai Party's policy steering chairman. The Somchai draft came about after a signature campaign garnered more than 64,000 signatures.
Mr Sutin said the main opposition Pheu Thai Party, of which he is a deputy leader, has sponsored three of the five drafts.
The joint sitting will deliberate all five drafts during the same session, although each will be individually endorsed. Parliament is expected to deliberate the drafts until midnight today and midnight tomorrow, according to Mr Sutin.
He said similar drafts had been proposed to parliament to scrap the Senate's prime minister-picking power, but none was successful.
But Mr Sutin said he believes more lawmakers will come to their senses and fulfil people's wishes to see the Senate let go of such a role.
"We're more hopeful despite the failures in the past," he said.
Sutin: Hopefulof change
Mr Sutin admits it is difficult for senators to cut their own powers. The drafts will not see the light of day without Senate support, he said.
Chief government whip Nirote Sunthornlekha agreed the drafts stand to be rejected by senators.
Mr Somchai, meanwhile, said he trusts the MPs will rally behind his amendment draft while the Senate might need to wait for a political "signal" before voting on it.
He added senators should not avoid the joint session. Instead, they should attend the meeting and show whether they support, reject or abstain from voting on the draft, he said.
The amendment, if passed, would retain Senate's neutrality in politics and enable the next government to be formed free of influence from an un-elected Senate.