Police are gathering evidence to take legal action against protest leaders and participants who turned up at city rallies on Thursday in violation of the emergency decree, says the deputy Royal Thai police spokesman.
Pol Col Kissana Phathanacharoen said the protesters also violated a health safety announcement issued by the Bangkok Metropolitan Administration.
Bangkok has been designated a Covid-19 maximum and strict control zone, with a ban on gatherings of more than 50 people.
Hundreds of demonstrators gathered on Thursday at the Democracy Monument in Bangkok to mark the 89th anniversary of the June 24, 1932 revolution. They also rallied on Ratchadamnoen Avenue last night.
About 500 people, led by activists Jatupat "Pai Dao Din'' Boontaraksa, human rights lawyer Arnon Nampa, Panupong "Mike" Jadnok, Atthapol "Khru Yai'' Buapat and Promsorn Veerathamjaree, began the rally on Ratchadamnoen Avenue.
Demonstrators wrapped a huge cloth banner around the monument before lighting candles in remembrance of the June 24, 1932 revolution by Khana Ratsadon that transformed Thailand from an absolute monarchy to constitutional monarchy.
Another group calling itself "Re-solution" set up a table to collect signatures in support of a bid to amend the constitution to remove the Senate and scrap the 20-year national strategy and reform plan. Some 46,781 signatures were gathered as of Thursday. The constitution allows the submission of a draft amendment supported by at least 50,000 people for consideration by parliament.
The "Prachachon Khon Thai" group led by activist and lawyer Nitithorn Lamluea also marched to Government House to demand the resignation of Prime Minister Prayut Cha-o-cha. The protesters were blocked by crowd control police at Chamaimaruechet Bridge. Police had two water canon and detention trucks on hand in case trouble flared.
However, the "Prachachon Khon Thai" group later moved to Nang Loeng intersection. Mr Nitithorn said he received reports that a third party would instigate violence. The group will gather again tomorrow. The "Thai Mai Thon" (Impatient Thais) group led by red-shirt leader Jatuporn Prompan also marched to Government House. The group dispersed at about 8pm and Mr Jatuporn said the group would gather again tomorrow at Phan Fa Bridge. There were no reports of violence as of press time.