Activist and academic Suda Rangkupan said Tanyawut Taweewarodomkul was freed from Bangkok Remand Prison today.
Tanyawut designed a website associated with Thailand's Red Shirt movement. He was convicted in 2010 of insulting the monarchy by posting defamatory comments against Thailand's King Bhumibol Adulyadej, and allowing such comments to be posted.
Thailand's law protecting the monarchy from defamation, or lese majeste, is the world's harshest. It mandates a jail term of between three to 15 years.
Tanyawut was sentenced to 10 years for two counts of lese majeste and another three for violating Thailand's Computer Crime Act. The royal pardon came after he had served three years.