Thai Prime Minister Abhisit Vejjajiva has put the head of the army in charge of national security.
In a televised address on Friday, Mr Abhisit said General Anupong Paojinda would be in charge of restoring order, replacing Deputy Prime Minister Suthep Thaugsuban.
Thousands of anti-government protesters demanding that Mr Abhisit dissolve parliament and call fresh elections remain camped in central Bangkok. Earlier efforts by police to arrest their leaders failed.
Last weekend the government tried unsuccessfully to clear them from part of the city. The crackdown failed, leaving left 23 people dead and more than 800 injured.
The BBC reports that General Anupong said on Monday that a political solution was needed to bring an end to the crisis.
