
More Photos
At least six people have been killed and scores injured in clashes in recent months.
The protesters — who seek to eliminate the one-person, one-vote system — is also seeking to purge the nation of the influence of former Prime Minister Thaksin Shinawatra. They accuse Thaksin of massive corruption and seeking to undermine the country's revered constitutional monarch, King Bhumibol Adulyadej.
Thaksin was ousted by a September 2006 military coup, but the alliance alleges that governments voted into office since then have been proxies for the exiled Thaksin.
"The PAD will return if another (Thaksin) proxy government is formed or anyone tries to amend the constitution or the law to whitewash some politicians or to subdue the monarch's royal authority," one of the protest leaders, Sondhi Limthongkul, warned Tuesday night.
The country's Constitutional Court found Somchai's People's Power Party, the Machima Thipatai party and the Chart Thai party guilty of committing fraud in the December 2007 elections that brought the coalition to power.
"Dishonest political parties undermine Thailand's democratic system," said Constitutional Court President Chat Chalavorn.
The ruling sent Somchai, Thaksin's brother-in-law, and 59 executives of the three parties into political exile, barring them from politics for five years. Of the 59, 24 are lawmakers who will have to abandon their parliamentary seats.
"It is not a problem. I was not working for myself. Now I will be a full-time citizen," Somchai told reporters following the ruling.
Government spokeswoman Suparat Nakboonnam said Deputy Prime Minister Chaowarat Chandeerakul automatically took over Somchai's job pending selection of a caretaker prime minister. She said Parliament would have to endorse the pick within 30 days.
A meeting Wednesday among the three ousted parties, which vowed to stick together in a coalition, was being held in a northern Bangkok suburb and it was unclear when they would decide on the caretaker prime minister.