A Thai woman sentenced to 43 years in prison for defaming the monarchy was released on Wednesday under a royal pardon, after serving just under one-fifth of her sentence, the Thai Lawyers for Human Rights said.

The human rights organisation added that 69-year-old Anchan Preelert was among the six political prisoners freed under a pardon issued on July 29 to mark King Maha Vajiralongkorn's birthday.

A former civil servant, Anchan had been sentenced four years ago in January by the Bangkok Criminal Court on 29 counts of violating Thailand’s lese majeste law for posting audio clips on Facebook and YouTube that were deemed critical of the monarchy, news agency AP reported.