The Thai-born US citizen jailed for posting online his translation of a banned book about the King was granted a royal pardon and freed on Tuesday, the United States embassy said.
Gordon: Released on Tuesday
"We are pleased that His Majesty granted US citizen Joe Gordon a royal pardon, which allowed him to be released from prison on Tuesday," embassy spokesman Walter Braunohler said.
"The US has the utmost respect for the Thai monarchy. As for Mr Gordon's plans from this point forward, due to privacy considerations we have no further comment at this time," he added.
In his latest interview with the Bangkok Post in early May, Mr Gordon, 55, said he was looking forward to a royal pardon since confessing to the lese majeste crime in October 2011.
The former car salesman from Colorado was convicted for posting a translation of excerpts from the book The King Never Smiles, which is banned in Thailand, on a blog he set up in the US under the pseudonym Nai Sin Sae Jiew.
Mr Gordon, or Lerphong Wichaikammart, was arrested in May 2011 in Nakhon Ratchasima while visiting Thailand.
Facing a complicated court process and the prospect of spending a long time in prison if he was refused bail, Mr Gordon pleaded guilty to the lese majeste charge.
He was sentenced to five years in jail, reduced to two-and-a-half years because of his confession.
When asked on previous occasions what he would do if pardoned, Mr Gordon said he was advised to leave the country as soon as possible.
He said he would like to stay longer in Thailand but felt uncertain about the political situation and his safety.
Mr Gordon could not be reached for comment after he was freed on Tuesday.
He left behind a handful of fellow lese majeste inmates at the Bangkok Remand Prison.
They include Surachai Danwattananusorn, NorPorChor USA webmaster Thantawut Thaweenarodomkul, Warawut Thanangkoon or Suchart Nakbangsai, shoe repairer Suriyan Kokpuey, CD vendor Sathien Rattanawong and Wanchai Tanprasert, a Singaporean serving a 10-year term.