Earlier the protesters, who had gathered outside the building since Sunday evening, dared government politicians to pass through their barricades.
"Politicians trying to go in may be hit by slingshots or harmed by some hot-headed people, which would tarnish the country's image"
Chai Chidchob, speaker of Thai parliament
"If they want to go in, they have to walk through us, including the prime minister,'' Chatuporn Prompan, a protest leader, , told reporters.
The protest has sparked fears of renewed unrest in Thailand after months of protests led by the anti-Thaksin People's Alliance for Democracy paralysed the previous government.
Those protests climaxed with an eight-day seizure of Bangkok's airports, virtually shutting down air links to the country and costing the Thai economy millions of dollars in lost earnings.
The group behind the current protests, which calls itself the Democratic Alliance against Dictatorship, is hoping to pressure the government to dissolve the parliament and call snap general elections.
It says Abhisit – Thailand's third prime minister in the space of just four months - came to power in a virtual coup d'etat.
Many of the protesters outside the parliament building in Bangkok carried signs reading "Give us back real democracy" and "Government of treason".