The Pheu Thai Party has called for the immediate release of former Samut Prakan MP Worachai Hema who was taken by the military for an "attitude adjustment" on Saturday, and demanded the government clarify its action.
A statement from the party said a group of soldiers led by Col Arthit Deeprasert, chief-of-staff of the 2nd Artillery Regiment, went to Mr Worachai's house in Samut Prakan's Muang district and took the former MP away in a white van to an unknown destination.
The party was closely following the situation with concern because the action by the military under the supervision of the government was unlawful and a serious violation of human rights, the statement said.
"If Mr Worachai had committed any legal offence, he should have been treated according to legal procedures. In this case, he has not been properly charged."
The party also called for the government to respect the people's right to honest expression of opinion.
"Since the coup in 2014, hundreds of politicians, academics, media members, students and people in general have been arrested for 'attitude adjustment', and more than 1,500 people have been arrested and indicted in the military court. More than 200 websites have been closed and many television and radio stations shut down.
"What the government has done is a gross violation of human rights and liberties of the people," the party said.
Pheu Thai said Mr Worachai had expressed his opinion to the public with honesty and without causing unrest in the country.
"His interview given on March 24 calling for the prime minister to show responsibility if the draft charter does not pass the public referendum is legitimate and in line with ethical standards recognised internationally," the party said.
The party demanded the government clarify the action taken against Mr Worachai, saying it was not theway to solve conflict in the country.