The revised amnesty bill has sent a wake-up call to the government's opponents, from the Democrat Party to the Green Politics Group, who have vowed to stop it.
The governing Pheu Thai Party appeared taken aback by the hostile reaction to the changes in the bill, which critics claim were clearly intended to help fugitive former prime minister Thaksin Shinawatra.
Worachai Hema, the Samut Prakan Pheu Thai MP who sponsored the original bill, attempted to placate opponents, saying MPs could always make further changes when it comes back to the House for second and third readings.
The bill was approved on Friday in an 18-5 vote by a Pheu Thai-dominated scrutiny committee. Dates for second and third readings in the House have not yet been set.
Democrat Party spokesman Chavanond Intarakomalyasut said all party branches would be directed to mobilise members to show their opposition to the bill.
"If the government still insists on doing anything to help one person, that will lead the country to a make-or-break situation and let's wait for that day to come," Mr Chavanond warned, referring to Thaksin.
The main source of controversy is Section 3 of the seven-section bill, which defines which offences would be covered by the proposed amnesty.
The section as amended by the scrutiny panel seeks to expand amnesty to include people found guilty by groups or "organisations set up after the military coup on Sept 19, 2006".
That definition would cover decisions by the now-defunct Assets Scrutiny Committee that was appointed to investigate alleged irregularities of the Thaksin administration, as well as those of the National Anti-Corruption Commission, which took over the ASC's cases.
It also seeks to absolve all people involved in political unrest, including soldiers, protest leaders and authorities.
However, those found guilty of lese majeste offences under Section 112 of the Criminal Code would be excluded from the revised section's coverage.
Mr Worachai's original bill covered the period between Sept 19, 2006 and May 10, 2011. It seeks to exclude Thaksin, the protest leaders and authorities responsible for crackdowns but include all others previously convicted of crimes relating to political violence.
In the revised Section 3 proposed by Prayuth Siripanich, a former Pheu Thai MP for Maha Sarakham, the coverage period runs from 2004 to Aug 8 this year.
The bill was interpreted by the Democrats as a legal manoeuvre to whitewash Thaksin and could be linked with attempts to return the 46 billion baht in assets seized from him.
The ASC investigations led to a Supreme Court ruling in 2010 to seize the assets from Thaksin's family after it found that he had abused his power to benefit the telecom business he controlled.
Suriyasai Katasila, co-ordinator of Green Politics, said his group would not let the draft bill become law "at all costs". He called it "the murderer of the rule of law".
The group will disclose its strategy in detail on Sunday, he said.
"Attempts [to use the draft bill] to whitewash Thaksin were not beyond expectations as the public knows that the ultimate goal is to give him amnesty and bring him home smartly," he said in a statement released on Saturday.
Pheu Thai members sought to mollify their opponents amid concern that the bill would be used to bring protesters back on the streets against the government.
The bill was aimed at bringing justice to the country, said Udomdet Rattanasathien, an adviser to the government whip. Talk of benefits for Thaksin was only a legal interpretation by critics, he added.
He urged the panel members vetting and approving the bill to explain to the public what their intentions were so that people would better understand the real goal.
Pheu Thai deputy spokesman Anusorn Iamsa-ard tried to ease concerns, saying the committee's decision should be respected. He asked critics not to over-react as the parliamentary process still had more stages left.