Groups of demonstrators staged rallies against Prime Minister Prayut Chan-o-cha over his eight-year tenure on Tuesday.
At Lan Khon Muang in front of City Hall, many demonstrators rallied to put pressure on Gen Prayut over his term limit.
Political activist Jatuporn Prompan said his group would stay at the site until midnight to start the countdown for Gen Prayut. The rally will be peaceful, he insisted.
Some 120 red-shirt protesters gathered at the Democracy Monument on Ratchadamnoen Avenue and started a ritual to put a curse on military dictators at 5.05pm. The protesters used one of the lanes to hold the ritual.
Ngernta Khamsaen, a leading member of the "Talu Khook 100%" group, delivered a speech on the stage, saying her group would also stay until midnight.
At around 5.25pm, Kanlamon Sunantharat, another leading demonstrator, began the curse ritual with about 50 demonstrators taking part in it. Other demonstrators observed the activity on pavements.
Three more protest groups - Rassadorn Lai Tu, Ronin Fangthon Mai Oao Padetkarn and Achiwa Pithak Prachachon Pue Phrachathippatai - also joined the anti-Prayut demonstration at the Democracy Monument.
The Daeng Kao Na group also gathered at the monument and leading protesters said they would march to Lan Khon Muang on Tuesday night.
Police had blocked off routes to Government House with shipping containers and rolls of razor wire on Tuesday morning ahead of rallies by many groups of protesters against Gen Prayut. Containers were also placed on Chamai Maruchet Bridge on Phitsanulok Road, opposite Government House.
