The Pheu Thai Party is binding its MPs to vote on party lines on the blanket amnesty bill, but claims it will not punish red-shirt MPs who oppose it.
The governing party says it has also reached a deal with its coalition partners to push the legislation through.
All party MPs have been told to suspend their engagements tomorrow to ensure they are present for the bill's second reading in parliament.
Speaking after a party meeting yesterday, Pheu Thai's secretary-general Phumtham Vejjayachai announced the party's intention to present a united front in support of the revised amnesty bill.
The party agreed to maintain a good relationship with those red-shirt figures who have openly opposed the bill, Mr Phumtham said.
Party leader Charupong Ruangsuwan said there was no need to threaten MPs who vote against the bill, as the party has rules and ways of dealing with offenders.
He did, however, concede that there were certain red-shirt MPs who did not agree with the amnesty plan.
A party source quoted former prime minister Somchai Wongsawat as telling yesterday's meeting that any MP who votes against the amnesty bill would forfeit their chance to run under the Pheu Thai banner in the next general election.
The revised version of the bill approved by the House scrutiny committee would grant an amnesty to all people involved in recent political unrest, including protest leaders, soldiers, and authorities responsible for ordering the 2010 crackdowns on the red shirts. The original covered only rank-and-file protesters.
The revised clause is believed to cover people facing legal action stemming from investigations into the 2006 coup, including several cases against ousted prime minister Thaksin Shinawatra.
Former interior minister Pokin Polakul, who now serves as an adviser to the prime minister, insisted the amnesty bill does not violate the constitution. He was "certain" the bill would survive Constitution Court scrutiny if critics filed a petition with the court.
"The bill is not a charter amendment draft but an amnesty bill," he said.
Meanwhile, Prime Minister Yingluck Shinawatra yesterday attempted to distance herself from the amnesty push, stressing that the bill is being pushed by only certain members of parliament and not the entire government.
The power of the government and that of legislators should be viewed separately, she said. The government was working to maintain peace in the country while the amnesty bill was the business of MPs and senators, she said.
In response to opposition leader Abhisit Vejjajiva's remark that she was "stubborn" in downplaying her role in the amnesty push, Ms Yingluck said she was sure Mr Abhisit was well aware that the government's power and the power of legislators were separate.
"The probes into the facts [about the 2010 violence] and the amnesty matter should also be considered as being separate," Ms Yingluck said.