He was arrested in December 2016 for sharing a profile by the BBC's Thai-language service of King Maha Vajiralongkorn, who took the throne after the death of his father, King Bhumibol Adulyadej. The profile included mentions of the king's past personal life that are not openly discussed in Thailand.
A crowd of family and friends greeted Jatupat as he was released from the prison in the northeastern province of Khon Kaen. Friends sang songs and clapped along as they posed for photos with him. Five members of Thailand's royalist Yellow Shirt movement who led a takeover of the prime minister's office in 2008 were also released Friday under the same amnesty, which was announced April 21 to mark Vajiralongkorn's formal coronation on May 4.
Jatupat's arrest was the first under Thailand's strict lese majeste law, which prohibits criticism of the monarchy, after Vajiralongkorn succeeded his late father. Critics of the law, which carries a punishment of up to 15 years' imprisonment per incident, say it is used to silence political dissidents.
Jatupat was initially given a five-year sentence, but because he pleaded guilty it was halved, a standard procedure in Thai courts. He had been denied bail 12 times and decided to plead guilty as a practical measure to get out of prison sooner, his father said after his sentencing.
Jatupat, now 28, had been a member of Dao Din, a small student organization that has protested against Thailand's military government, which took power after the army staged a coup in 2014. He was put under close watch by Thai authorities after November 2014, when he and several other Dao Din members used a three-fingered salute, a resistance gesture borrowed from "The Hunger Games" movies, during a speech by Prime Minister Prayuth Chan-ocha, chief of the military junta. He was also among about a dozen students arrested in June 2015 for participating in anti-government protests.
Prosecutions under the lese majeste law became more frequent under the junta, but appear to have trailed off in the past couple of years. Thailand held a general election in March, but no single party won enough seats to form a government on its own. Critics say the military held the polls under rules made to favor its allies, and Prayuth is generally expected to become prime minister again by early June, after the new parliament convenes.