Analysts say pro-Thaksin lawmakers would probably win if elections were held today. At the last elections in December 2007, the now-defunct People's Power Party won 233 out of 480 seats in parliament.
The reds lost credibility, though, when the April protests descended into chaos. Some liberals are turned off by Thaksin, a billionaire businessman who won landslide election victories in 2001 and 2005. Last year he was convicted of abusing power, and his two terms were shadowed by human-rights abuses.
After nearly four years of upheaval, Thais are disenchanted by politics in general: only 31 percent think the country is moving in the right direction, according to a survey by the Asia Foundation.
Who was behind last year's protests? Could they start again?
The People's Alliance for Democracy (PAD) wears royalist yellow and was formed in 2006, when Thaksin was in power. Its leaders include a media tycoon, a former mayor, and a trade unionist. Its followers are mostly conservatives who fear losing privileges under strong elected governments.
Last year, the PAD held nonstop protests for several months. It draws support from the upper and middle classes in Bangkok and southern Thailand (though not the insurgency zone), as well as from individuals in the palace, military, and civil service. While largely peaceful, it had armed security guards.
The protests peaked with the weeklong seizure of Bangkok's two airports. After the courts dissolved the government, the PAD told its supporters to go home. It later registered its own New Politics party.
In April, PAD leader Sondhi Limthongkul survived an assassination attempt that he blamed on rogue Army officers. No arrests have been made.