Thai Prime Minister Abhisit Vejjajiva has announced he is putting the country’s army chief in charge of security operations.
In a televised address, he said Gen Anupong Paojinda would be in charge of restoring order, replacing Deputy Prime Minister Suthep Thaugsuban.
The announcement came as tens of thousands of anti-government protesters remained camped out in central Bangkok.
Earlier in the day efforts by police to arrest their leaders failed.
The red-shirt protesters are demanding that Mr Abhisit dissolve parliament and call fresh elections.
Last weekend the government tried unsuccessfully to clear protesters from part of the city. The failed crackdown left 23 people dead and more than 800 injured.