Thailand's army chief announced in an address to the nation on Thursday that the armed forces were seizing power after months of deadly political turmoil.
"In order for the country to return to normal quickly the National Peace Keeping Committee comprised of the army, the Thai armed forces, the Royal Air Force and the police need to seize power as of May 22 at 4.30 pm," army chief Prayut Chan-O-Cha said.
He said the takeover would not affect international relations.
Thai soldiers earlier took the leader of anti-government protests out of a meeting of all factions, witnesses said.
Hundreds of extra troops arrived at the venue from where Suthep Thaugsuban, who has been leading more than six months of anti-government protests, was taken away.