Police have summoned two leaders and 26 other people involved in Sunday's protest against Prime Minister Prayut Chan-o-cha to answer a slew of charges that could also include lese majeste.
Red-shirt leader Jatuporn Prompan, who organised the mass gathering on behalf of the "Thai Mai Thon (Impatient Thais)" group and Adul Khiewboriboon, leader of the Samakkhi Prachachon group, will be among 14 people summoned to meet investigators and answer charges next Thursday, Pol Maj Gen Piya Tawichai, deputy commissioner of the Metropolitan Police Bureau said on Wednesday.
The other 14 people will be summoned to answer charges the following day, he said.
Twelve other people who had a role in the rally at Santiporn Park that spilled over into Monday were also found to have violated several laws and will soon be summoned to face charges as well, he said.
The protest was held to demand Gen Prayut's resignation.
Pol Maj Gen Piya reiterated that all public gatherings are now considered unlawful under the emergency decree and the disease control law, being implemented to contain the spread of Covid-19.
"Not only protest leaders but also anyone who takes part in such public gatherings and those who support the staging of them could face legal action for violating these laws," he said.
The police were also examining a recording of a speech Mr Jatuporn delivered at Sunday's gathering to determine whether comments made violated Section 112 of the Criminal Code, the lese majeste law, said Pol Maj Gen Piya.
Sonthiya Sawasdee, adviser to the House committee on law, justice and human rights, on Tuesday asked police at Chana Songkhram station to look into Mr Jatuporn's speech.
In related news, the Criminal Court on Wednesday inspected lists of witnesses and pieces of evidence in a lese majeste case against 22 protest leaders including Parit "Penguin" Chiwarak in connection with rallies at Thammasat University's Tha Phrachan campus and Sanam Luang on Sept 19-20 of last year.
Kritsadang Nutcharat, a lawyer with the Thai Lawyers for Human Rights Centre, who represented the 22 defendants, said one piece of evidence was a video clip.
Mr Kritsadang said he watched the video clip on Wednesday and found nothing in it that suggested his clients had violated any laws.
He added he was confident that the court will determine that what was captured in the clip was nothing more than lawful criticism.