Democrat MP for Surat Thani Suthep Thaugsuban on Tuesday declared he will mobilise supporters nationwide to oppose the bill.
The party's executives met yesterday following House Speaker Somsak Kiatsuranont's decision to call a meeting of the House on Thursday to deliberate the revised amnesty bill.
Mr Somsak's urgent letter, dated Oct 29, says the special House meeting will begin at 9.30am.Democrat deputy leader Thaworn Senneam said the party will organise a mass rally at Samsen railway station tomorrow evening, and has asked its MPs to call demonstrations in their own provinces before leading rally goers to join the main protest site in Bangkok.
The opposition executives resolved the party's four deputy leaders in each region will resign from their positions as executive directors to lead the rally.
They are Korn Chatikavanij for Bangkok, Issara Somchai for the Northeast, Siriwan Pratsajaksatru for the North and Mr Thaworn for the South.
The new version of the bill approved by a House scrutiny panel offers a blanket amnesty for all those involved in political protests from the Sept 19, 2006 coup to Aug 8, 2013, except those accused of violating Section 112 of the Criminal Code, also known as the lese majeste law.
Mr Suthep said he was asking people nationwide to unite against the bill.
"We will stake our lives on it," Mr Suthep said during a press conference to counter the order of the Office of the Attorney-General (OAG) to indict him and Mr Abhisit on murder charges in connection with the Democrat government-ordered crackdowns on red-shirt protesters in April-May 2010.
Mr Suthep said the campaign against the amnesty bill will remain within the law and not involve the use of weapons or the torching of buildings.
"We are not terrorists. We will not use weapons to fight anyone and we will not burn down buildings.
"We will stage sit-ins at provincial halls as an act of civil disobedience against the government," he said.
Mr Suthep said Prime Minister Yingluck Shinawatra must order the Pheu Thai Party to withdraw the amnesty bill. He said the prime minister is in a position to head off any conflict and she should stop skirting around the issue.
If Ms Yingluck still put the interests of her elder brother Thaksin Shinawatra and her family before the nation's, "you will end up without a country to live in", Mr Suthep warned.
Regarding the OAG's indictment order, Mr Suthep said public prosecutors had acted as a government tool in pressuring him and Mr Abhisit to accept the bill offering a blanket reprieve.
Mr Suthep said the OAG's decision to prosecute them, which is based on the recommendation of the Department of Special Investigation (DSI), is questionable. The OAG on Monday said the case involves extra-judicial killing offences, not an offence regarding abuse of authority which would have been investigated by the National Anti-Corruption Commission. This gave the DSI the authority to investigate the case.
However, Mr Suthep said it was strange the OAG and the DSI did not charge them with abuse of authority under Section 157 of the Criminal Code, which is the standard charge brought against a state official exercising authority.
The OAG and the DSI argued that Mr Abhisit and Mr Suthep did not order the crackdowns on the protesters in their capacities as prime minister and deputy prime minister.
But Mr Suthep said that if he and Mr Abhisit had not been in those posts at the time, they could hardly have ordered crackdowns.
Mr Suthep was the deputy prime minister and the director of the now-defunct Centre for the Resolution of the Emergency Situation during the red-shirt protest period, acting on behalf of Mr Abhisit who was prime minister at the time.
While the Democrats cannot fight Pheu Thai's commanding majority in the House, they will petition the Constitution Court against the bill, Mr Abhisit said, declaring he was ready to fight all of the cases against him all the way to the Supreme Court.
He also said he and Mr Suthep had previously filed a lawsuit against DSI chief Tarit Pengdith for abusing his authority when the DSI recommended prosecutions against them.
They will file a similar lawsuit against the OAG, Mr Abhisit said.
Mr Tarit on Tuesday insisted the DSI's investigation was straightforward and based on evidence.