The outgoing senators - Nirun Phitakwatchara of Ubon Ratchathani and Karoon Saingam of Buri Ram - and People's Alliance for Democracy (PAD) leader Somsak Kosaisuk filed the criminal suit against EC chairman Vasana Puemlarp and members Prinya Nakchudtree, Virachai Naewboonnien and Charupat Ruangsuwan, saying they failed to organise last month's general election honestly and fairly.

The plaintiffs said the commissioners should not have allowed the election to be called so quickly and that the EC illegally changed the positions of the ballot booths and the design of the ballot itself.

Moreover, they allowed the posting of numbers and photographs of candidates in front of the ballot booths and allowed more candidates to join the second round of voting in constituencies where standalone candidates failed to meet the 20-per-cent of the vote requirement in the first round.

The plaintiffs also called on the court to cancel the defendants' right to vote for 10 years.

The court accepted the case and will hold a first hearing on June 5.

Lawyer Varin Thiemcharas, who is secretary-general of the People's Network for Elections in Thailand, said the highest penalty the court could hand down to the defendants was 10 years in prison.

Another PAD leader, Somkiart Pongpaiboon, said he and others had filed the same lawsuit against the commissioners with the court in Nakhon Ratchasima.

Meanwhile, Senator-elect Uthai Pimchaichon said yesterday he would submit a resignation letter for the election commissioners to sign at their office today.