Roads around Ratchaprasong intersection were being closed on Sunday for a rally called by a group of anti-government allies after Prime Minister Prayut Chan-o-cha refused to step down.
At least 1,000 anti-government protesters were occupying Ratchadamri Road outside the CentralWorld shopping complex at about 4pm for a demonstration to pressure Gen Prayut to cede power.
They gathered in shopping malls around the area to wait for the rally to begin.
The rally is the first since the prime minister ignored the deadline of 10pm on Saturday imposed by the protesters. Another major rally will be held at Samyan intersection on Monday. They warned of accelerated measures to pile more pressure on Gen Prayut to quit his position.
Pol Lt Gen Pakkapong Pongpetra, commissioner of the Metropolitan Police Bureau, urged protesters maintain a peaceful gathering and reminded them ot observing social distancing measures to prevent the spread of Covid-19.
He said police will not allow confrontations with royalists and people opposing the rally.
A group of people dressed in yellow gathered outside Parliament and pledged to camp out there to pressure lawmakers to keep reform of the monarchy off the agenda in a two-day special parliamentary session starting on Monday.
A Suan Dusit Poll released on Sunday showed most people think the government should hold talks with protesters, while a Nida survey by the National Institute of Development Administration said respondents were worried by the continued rallies.
