He said the Democrat Party believed the election contravened the Electoral Act and the Constitution. The party will gather evidence of wrongdoing and submit a request with the Office of the Ombudsman, asking it to approach the Constitution Court.
The request would be separate from the one submitted earlier by Wirat Kallayasiri, chief of the party's legal office.
Mr Ong-art called on the government to lift the emergency decree imposed in Bangkok and surrounding provinces. Now that the Feb 2 election, a reason for imposing the decree, is regarded as over, it was no longer necessary to keep the decree in force. Moreover, it was evident that the protests had not caused violence to a point where an emergency situation was justified.
The decree, he said, would only erode confidence in the country's economy and tourism, Mr Ong-art said.
On the election, Mr Ong-art said it was unlikely parliament would open and a new prime minister named and a new government appointed in five to six months from now, causing Thailand lost opportunities.
He said the government had insisted on holding the election to retain power for as long as possible.
Moreover, the government hoped to use the election results to claim that the majority of people still support it and to win support from the international community, Mr Ong-art said.