The Foreign Office was already advising against all but essential travel to Bangkok amid the anti-government “Red Shirts” protests that have rocked the city in recent weeks.
But officials decided to close the Bangkok embassy temporarily “due to its proximity” to the demonstrations.
Tensions were heightened on Thursday after a renegade army general, Major General Khattiya Sawasdiphol, who was backing the protesters, was shot in the head in the street as he spoke to foreign reporters.
Soldiers reportedly shot a second person dead and at least three other people were injured in the ensuing clashes in which hundreds of protesters threw rocks and firecrackers.
A Foreign Office spokeswoman said: “The UK embassy will be closed to the public on Friday due to its proximity to the demonstrations in central Bangkok. Our embassy will continue to monitor developments in Bangkok in order to provide British nationals with the most up-to-date information.
“British nationals in Thailand requiring consular advice can continue to contact our embassy via our telephone hotline, which is staffed at all times. We will keep the situation under review.”
The Red Shirts protesters are occupying a historic district of Bangkok to put pressure on prime minister Abhisit Vejjajiva to resign and call elections. They believe the coalition government came to power illegitimately through manipulation of the courts and the backing of the powerful military.
Maj Gen Khattiya was accused of creating a paramilitary force among the demonstrators. Before he was shot, people were urged to leave the area near the protesters’ sprawling camp, and shops and businesses were advised to close.
In an attempt to stop protesters joining a massive anti-government rally in the capital, the Thai government also extended its state of emergency to cover 17 provinces.