A Thai welder has been sentenced to more than 11 years in prison for insulting the royal family in a series of online posts.

Burin Intin was charged with lese majeste – insulting the Monarchy – after posting a “defamatory” comment on Facebook and in a private message. The crime carries a maximum penalty of 15 years in prison in Thailand.

The 28-year-old was also convicted under the Computer Crime Act which prohibits putting “false data” on a computer, raising fears the state was monitoring his private correspondence.

Burin was originally sentenced to 22 years, eight months, however his guilty plea meant his sentence was halved to 11 years, four months.

The activist was arrested in April 2016 while attending a protest against other activists’ arrests with pro-democracy group Resistant Citizens.

He was accused of sending a message that defamed the monarchy to the mother of a pro-democracy activist, Patnaree Chankij.

Patnaree was also charged with lese majeste in May for not denouncing Burin and will be tried in a military court in March, according to local media.

Critics have long accused the government of using the law to intimidate critics.