In the fraud case linked to PPP, the Court cited the July 8 Supreme Court conviction of former House speaker Yongyuth Tiyapairat, also former deputy PPP leader, over vote-buying in last December 23 general election, which saw PPP win most votes, as the ground to disband the ruling party.

Yongyuth was banned from electoral process for five years.

Under Thailand's Election Law under the 2007 Constitution, if any executive member of a political party committed electoral fraud, the party could be dissolved and its executive committee will be banned from engaging in political activities for five years.

The Court then cited earlier rulings by the Election Commission which held Chart Thai party executive Monthien Songpracha and Sunthorn Wilawan of Matchima Thipataya guilty of electoral fraud as basis to convict the two parties.

The nine presiding judges reached unanimous decisions against PPP and Matchima, while voted eight-to-one to convict Chart Thai.

The two parties were among the five political parties that partnered with the PPP to form the coalition government, then headed by Samak Sundaradej this February. Samak was removed in September over a court verdict for hosting a TV cooking show while in office.

The verdict reading process took only some 40 minutes to complete, unexpectedly much swifter than the Court did in May last year to the former ruling Thai Rak Thai (TRT) party following the September 19, 2006 coup that ousted then premier Thaksin Shinawatra.

The TRT was disbanded on electoral fraud charges and its 111 executives including founder Thaksin Shinawatra were banned from politics for five years.

The PPP, which is seen by opponents as a reincarnation of the TRT, did not attend Tuesday's summation session, protesting that the judges were biased against the government.

Thai government supporters hold a rally to protest against Thai Constitution Court's order to dissolve the three ruling parties, in front of the Bangkok Intermediate Administrative Court in Bangkok December 2, 2008. [Xinhua]

PAD protesters, who had been rallying at the two airports in Bangkok in a showdown to topple the government, hailed as the Court handed down the verdict.

Since Somchai was disqualified, First Deputy Prime Minister Chaovarat Chanweerakul will become caretaker prime minister pending a meeting of the caretaker Cabinet, former PM's Office Ministers Sukhumpong Ngonkham said Tuesday.