BANGKOK –

An anti-government activist accused of burning a portrait of Thailand's King Maha Vajiralongkorn was arrested on Wednesday police said, the latest among dozens of people charged in recent months for insulting the monarchy.

Musician and activist Chaiamorn "Ammy" Kaewwiboonpan, 32 was arrested in Ayutthaya province north of Bangkok and is accused of setting fire to the portrait on Sunday in front of a Bangkok prison where four prominent activists are being held.

Chaiamorn is charged under a strict lese majeste law that carries a penalty of up to 15 years in prison if found guilty, as well as arson and trespassing on government property.

"We have both witnesses and forensic evidence," Bangkok police chief Pakapong Pongpetra told a news conference, adding Chaiamorn was not the only person suspected of involvement.

Chaiamorn was receiving medical treatment at a hospital for an injury unrelated to his arrest, police said.

His lawyer Sasinan Thamnithinan said he would be granted access to Chaiamorn later on Wednesday when police take a statement from his client.

Months of youth-led protest against the military-backed government of Prime Minister Prayut Chan-ocha last year also broke traditional taboos by calling for reform of the powerful monarchy.

At least 61 people have subsequently been charged with lese majeste, based on data compiled by legal aid group Thai Lawyers for Human Rights.

Four of those are prominent protest leaders currently in prison awaiting trial.

The portrait burning took place the same day, hours before protesters marched on a Bangkok military base to call for the king to give up direct control over army units transferred to him in 2019 by the government of Prayut, a former military chief.

Police used rubber bullets against the youth-led protesters for the first time on Sunday, as well as tear gas and water cannon.