Pro-democracy student leaders install a plaque declaring "This country belongs to the people" at the Sanam Luang field during a protest in Bangkok, Thailand, Sept 20, 2020. (SAKCHAI LALIT / AP)

BANGKOK - A plaque placed by Thai pro-democracy protesters near the Grand Palace in Bangkok that declared that Thailand belongs to the people and not the king has been removed, as police warned on Monday they may charge those behind the symbolic gesture.

The new plaque, which resembles one that had commemorated the end of absolute monarchy in 1932 and was removed from outside a royal palace in 2017.  Criticising the monarchy is illegal under lese majeste laws in Thailand 

The plaque was placed in the area known as Sanam Luang, or Royal Field on Sunday after a weekend rally by tens of thousands of people who cheered calls for reforms to the monarchy of King Maha Vajiralongkorn. 

The Fine Arts Department and the Bangkok Metropolitan Administration removed the plaque, and the cultural heritage agency also filed a complaint against the protesters for breaking the law on ancient monuments, according to district police chief Worasak Pisitbannakorn. Footage shared on social media showed fresh concrete at the spot where the brass plaque was installed during the weekend protest, the largest gathering since the 2014 military coup.

Government spokesman Anucha Burapachaisri said eariler that police would not use violence against protesters and it was up to the police to determine and prosecute any illegal speech.

At the biggest demonstration in Thailand in years, protesters cheered calls for reform of the monarchy as well as for the removal of Prime Minister Prayuth Chan-ocha, a former junta leader, and a new constitution and elections.

After the protest, people queued up to take pictures next to the plaque, which reads “At this place the people have expressed their will: that this country belongs to the people and is not the property of the monarch as they have deceived us” and also features a hand giving the three-finger salute adopted by protesters.

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But far from all Thais support the new plaque, which resembles one that had commemorated the end of absolute monarchy in 1932 and which was removed from outside a royal palace in 2017, after Vajiralongkorn took the throne. Prominent right-wing politician Warong Dechgitvigrom said on Sunday the plaque was inappropriate and the king was above politics.

“It didn’t achieve anything,” he told Reuters. “These actions are symbolically against the king, but the king is not an opponent.”

Craig Kunakorn, 33, a barber who had been at the protests came to visit the spot where the plaque had been cemented into the ground on Monday.

“Everyone knew it would disappear soon but the success of creating it is something that will continue. It is still an important symbol,” Craig said.

Anon Nampa, an activist and human rights lawyer, told Reuters the plaque should be returned to the people.

“We will go and file a complaint to police today to find that plaque which is the people’s property and who took it,” said Anon, one of the leading figures in the loosely organised protest movement.

Protesters have grown ever bolder during two months of demonstrations against Thailand’s palace and military-dominated establishment, breaking a longstanding taboo on criticising the monarchy - which is illegal under lese majeste laws.

The Royal Palace was not immediately available for comment. The king, who spends much of his time in Europe, is not in Thailand now.

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The demonstrators say the constitution gives the king too much power and that it was engineered to allow Prayuth to keep power after elections last year. He says that vote was fair. 

“Our nation, religion, and the king are important pillars for everyone in this country,” Prayuth said on Monday while thanking security officials for ensuring the weekend protests were peaceful. “If the country is peaceful, we can solve any problems.”

The next protest is scheduled for Thursday. Protest leaders also called on Thais to take Oct 14 off work to show their support for change.

Other measures they sought for were for people to withdraw deposits from Siam Commercial Bank SCB.BK, in which the king's Crown Property Bureau owns more than 23 percent of the shares, and to stop standing for the royal anthem in cinemas.