The Thai Journalists' Association voiced concern on Tuesday about the "damaging" of media rights following the arrests of a reporter and a photographer who covered an anti-monarchist graffiti incident last year.

The reporter -- who works for independent online outlet Prachatai -- and the freelance photographer were arrested on Monday over their coverage of the incident at Bangkok's Grand Palace complex in March last year.

They were charged with being accomplices in the damaging of a historic monument.

"The Thai Journalists' Association is concerned about the damaging of media rights and freedom," the group said in a statement.

"It was necessary for journalists to cover the news."

The arrests stem from an incident last March in which a man spray-painted an anarchist symbol and the number 112 with a line through it on the outside wall of Bangkok's Temple of the Emerald Buddha.

The act, caught on video, was widely reported in Thai media because the temple is part of a complex of historic royal buildings, and 112 is a reference to the kingdom's controversial lese-majeste laws.

Thai Lawyers for Human Rights, a legal rights group, said on the social media platform X that the pair were granted bail on Tuesday afternoon.

Prime Minister Srettha Thavisin said the reporters received fair treatment.

"Under this government, we have given space to the media to do their work," he told reporters.

Thailand ranked 106 out of 180 in the World Press Freedom Index in 2023.