BANGKOK -- Lawmakers in Thailand debated a political amnesty bill on Wednesday as anti-government protesters demanded it be scrapped because they say it will help exiled former premier Thaksin Shinawatra return home a free man.

Despite fears of a re-run of the violence that has marred Thai politics since 2006, the demonstration by the main opposition party was mostly peaceful and many of the estimated 2,500 protesters heeded a call by their leaders to disperse after police refused to let them approach parliament.

Anti-government protesters confront riot police officers outside the parliament in Bangkok August 7, 2013. Thailand's parliament was due to debate a political amnesty bill on Wednesday as anti-government protesters marched to try to get it scrapped, saying it could let ex-premier Thaksin Shinawatra return from exile without having to serve a jail sentence. [Photo/Agencies]

Thaksin was ousted by the military in 2006 and found guilty of abuse of power, fleeing the country before a two-year sentence was handed down. His sister, Yingluck Shinawatra, is now prime minister and critics says her government wants to find a way to get his conviction quashed so he can return without going to jail.

Opposition leader Abhisit Vejjajiva had earlier led the protesters towards parliament. "It's not about organising a mob but about spreading the truth to the people, to recognise the dangers of this amnesty bill, that there are different hidden agendas," Abhisit told his Democrat Party's Blue Sky News television channel.

Thaksin, a former telecommunications tycoon, is hugely popular among poor urban and rural people and he led his party to two big election victories before he was ousted. But he is mistrusted by the military-royalist establishment, who say he is corrupt and authoritarian.

Abhisit was prime minister during unrest in 2010 when Thaksin's red-shirted supporters tried to force early elections. More than 90 people, both protesters and security forces, were killed and Abhisit has been charged with giving orders to use live ammunition that led to civilian deaths.

SOME WORRY

About 4,800 police have been mobilised for the protests this week and an internal security act has been implemented to allow measures such as a ban on gatherings near parliament.

Financial market analysts have worried about the prospect of renewed unrest in Thailand, especially as coup rumours have resurfaced, and foreigners have sold stocks in recent sessions. But overall the Thai bourse edged up earlier this week and it was higher again in late trade.

The amnesty bill, sponsored by a lawmaker from the pro-Thaksin ruling party and backed by the government, would scrap convictions or charges involving protesters active in the waves of political unrest since the 2006 coup.

The draft bill does not provide for an amnesty for leaders of the various bouts of unrest but opponents argue it could be altered to achieve that as it makes its way through parliament. Specifically, they believe Thaksin's graft conviction could be done away with, allowing him to return home a free man.

The first reading of the bill is expected to be completed later on Wednesday and it will then be scrutinised by a 35-member committee.

Anti-Thaksin "yellow shirt" protesters helped undermine his government and two later governments that supported him in 2008. Their protests included occupying Bangkok's two main airports that year, halting flights for days. However, they have decided against joining this week's rally and have generally kept a low profile since the July 2011 general election won convincingly by Yingluck.