The Criminal Court on Monday jailed a freelance writer known as "Rung Sila" for four years and six months for lese majeste and violating the Computer Crimes Act.
The court originally jailed him for six years but reduced the sentence due to him giving prosecutors useful evidence. He was immediately freed due to time served.
Siraphop Korn-arut had been charged for work published on the "Prachathai" web board during 2009 and 2014. The contents deemed offensive to the monarchy were produced under the pseudonym "Rung Sila".
He was arrested following the May 2014 coup and was tried in a military court under an order of the now-dissolved National Council for Peace and Order (NCPO).
The case was later transferred to the Criminal Court, where he denied all the charges.
Mr Siraphop was remanded in custody for four years and 11 months before being finally granted bail in June 2019.
After the verdict, therefore, he was not sent back to prison and was deemed to have already served sufficient time behind bars.
He said after the hearing that although he was now free to go home, he would still appeal the conviction and sentence because the lese majeste law was being used as a political tool against critics of army coups.