The two People Power Party (PPP) MPs from rural constituencies have filed complaints, saying Thai Airways pilots on separate flights from Bangkok to northeastern cities would not let them board.

'As a state enterprise, Thai Airways has no policy to get involved in politics,' an airline spokeswoman said.

'The company has notified all pilots, but as a complaint was made, the airline is setting up a committee to investigate immediately.' She said Thai Airways had apologised to the lawmakers.

Ms Farida Sulaiman, a PPP lawmaker from Surin province, told Thai television that the pilot stopped her as she tried to board a plane early on Wednesday and told her that her presence on board could cause a disturbance.

Her fellow PPP lawmaker Chaiya Promma was also prevented from boarding a flight to Udon Thani early Wednesday, Thai Airways said.

Protesters from the anti-government People's Alliance for Democracy (PAD) attempted to seal off Thailand's parliament on Tuesday, prompting police to fire rounds of tear gas on the crowd.

More than 400 people were injured and two killed in the clashes.

In August the leader of a Thai Airways workers' union called on its 15,000 members to go on strike in solidarity with the ongoing PAD protesters, but few appeared to have heeded that call. -- AFP