The first mass rally since the lifting of some of the coronavirus-related restrictions is organized by a group calling itself Liberation Youth, which convened hundreds of young protesters through a call on social media.
People began to gather at the Democracy Monument at about 4.00 p.m. local time (09:00 GMT) and continued to rally until late at night. The protest's organizers, on behalf of the participants, put forward three demands to the government of Prime Minister Prayuth Chan-ocha, the former army chief who ousted an elected government six years ago.
The demands included the dissolution of parliament, an "end to harassment of government critics", and amendments to the military-written constitution followed by new elections.
"We will stay on this square until morning, and if we do not receive any response from the authorities, we will give them two more weeks to rewrite the constitution, and if this does not happen, we will again gather for a mass rally, and next time it will not be for a day," the movement's leader said.
The police soon cordoned off the square and constantly appealed to protesters to disperse.