The government shut down the privately owned satellite channel last month following the clashes.
It accused the channel of inciting violence and encouraging protesters to break the law during an aborted summit of Asian leaders in the resort town of Pattaya last month.
|Security has been stepped up in Bangkok for a summit on the H1N1 flu outbreak [AFP]
Several Asian leaders were forced to flee the summit by helicopter or hide in their rooms after anti-government protesters stormed the venue.
Thursday's protest came as the government stepped up security in Bangkok as health ministers from across Asia gathered for an emergency summit on measures to combat the H1N1 flu outbreak.
Thai officials are eager to avoid a repeat of the abandoned Pattaya summit, which was seen as highly embarrassing for the government.
The health officials will try to devise a binding resolution on pandemic preparedness and action plans to be submitted to the World Health Organisation (WHO) in Geneva, on May 18.