Three lawyers submitted a citizen's petition asking the Supreme Administrative Court to cancel the Royal Decree for the April 2 election.
The trio - Nitithorn Lumlua, Nakhon Chompoochat and Pairoj Pholphet - chose to litigate as individuals rather than involving their professional group, the Law Society of Thailand.
The three argued for the decree's cancellation on the grounds it was wrongfully enacted.
Under the Constitution and election law, the Election Commission is required to make a collective decision to schedule the election day.
But the government only consulted EC chairman Vasana Puemlarp before enacting the Royal Decree, the three said in their petition.
Because of the initial errors in calling the snap election, the ensuing electoral process was plagued by many flaws, which undermined the credibility of the election's outcome, the petition said.
Key flaws included the lack of voter privacy while marking their ballots, the overwhelming number of abstentions and invalid votes and the alleged fraud involving members of smaller parties being bribed to contest the poll.
The election outcome failed to represent the people's mandate as evidenced by the fact that in many constituencies there were more "no votes" cast than there were votes for the winners, the petition said.
Meanwhile the Democrat Party has also petitioned the Administrative Court to nullify the April 2 election as the ruling Thai Rak Thai government had illegally and too hastily called it.
This resulted in several flaws that left the country floundering, said Thaworn Senneam, deputy secretarygeneral of the party.
"The court has accepted our petition and we hope it will make an urgent ruling on this matter," he said.
His Majesty the King on Tuesday suggested the three courts - Administrative, Supreme and Constitution - help seek a way out for the ongoing political conflict.
The Democrats' petition came a day before the chiefs of the relevant courts were scheduled to discuss ways to resolve the political staleŽmate in response to advice handed down by HM the King.
The three courts were holding internal discussions today.
Meanwhile, Democrat Party leader Abhisit Vejjajiva said the petition was filed so the court could discuss the issues, given the fact that no court can raise any issue without a complaint or petition.
"Now the court will consider it. We are waiting for the ruling and we are ready to cooperate with the ruling.
The Democrat, Chat Thai and Mahachon parties boycotted the April 2 election, saying Thaksin's calls for the House dissolution and the election were not legitimate.
However, they said if the election is nullified and a new election is set, they will rejoin.
The Nation