Updated

Thailand's politics heated up Wednesday over a bill that could herald the return of divisive ex-Prime Minister Thaksin Shinawatra, while his former top lieutenants prepared to re-enter the political arena after a five-year ban.

The party of current Prime Minister Yingluck Shinawatra, Thaksin's sister, was hoping to introduce legislation in parliament Thursday that is widely seen as a possible first step toward providing amnesty for her fugitive brother's convictions and allowing him to return unencumbered to Thailand.

Thaksin had been ousted by a 2006 military coup after being accused of abuse of power and disrespect to Thai King Bhumibol Adulyadej. His party was dissolved by a legal decision the year after, and he was among the 111 executives of his Thai Rak Thai Party banned from politics for five years. He also was convicted in absentia of corruption while in self-imposed exile.

The prospect of Thaksin's return has galvanized his opponents inside and outside parliament, threatening to reopen political wounds from a six-year struggle between Thaksin's opponents and supporters.

His Yellow Shirt opponents in the People's Alliance for Democracy were back on the streets Wednesday in one of their largest demonstrations in recent months. They oppose a government-backed reconciliation bill to grant amnesty to all parties involved in political violence and wrongdoing from the end of 2005 through mid-2010, a period when Thailand was wracked by turmoil and street protests.

Yellow Shirts' protests in 2006 set the stage for the coup, and in 2008 they occupied the prime minister's offices for three months and Bangkok's two airports for a week to pressure two pro-Thaksin prime ministers out of office.

The street protests Wednesday were peaceful, but the scene was different in parliament, where police had to keep order as the opposition Democrat Party sought to derail efforts to schedule debate on the bill. At one point, a female Democrat lawmaker dragged the House speaker's empty chair off the podium, sparking a scuffle with government members of parliament. A phalanx of policemen retrieved the chair.

Meanwhile, the five-year ban on Thaksin and his party associates was set to expire at midnight Wednesday. The Constitutional Court in 2007 had ordered the Thai Rak Thai Party dissolved and its top members suspended from politics for five years. The court had found two senior members guilty of electoral law violations in 2006.

Thaksin's opponents sought to purge his influence after the coup, launching investigations of his finances and using other measures to try to cripple his political machine, which he built using a fortune made in telecommunications.

The re-entry into politics of Thaksin's party leaders was widely expected to lead to a reshuffle in the Yingluck's Cabinet, although many of the current members may be reluctant to give up their positions.

Karn Yuenyong, executive director of the independent, Bangkok-based research institute Siam Intelligence Unit, said the returnees could bring some valuable experience into the administration.

"This, in a way, will help the Yingluck government sail through its four-year term," Karn said, adding that some of the current ministers "have not been performing really well in the past few months."