Thanakorn Siripaiboon, 27, has been charged by police with lese majeste for a "satirical" Facebook post about the king and his dog, lawyer Pawinee Chumsri told AFP.
"There was a post including three photos on his Facebook page on December 6 with a message that satirised the king's dog," she said.
Thanakorn also faces lese majeste, sedition and computer crimes charges for clicking "like" on a doctored photo of the king and sharing it, plus an infographic on a growing corruption scandal engulfing the junta.
Prosecutions have soared since the army, which styles itself as the champion of the monarchy, grabbed power in a coup last year.
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Thanakorn, an auto-parts worker, could face up to 37 years in prison. There has been a recent trend towards record-breaking sentences on transgressors, many of whom are also regime critics.
Even the US ambassador faces a police investigation for royal defamation over a speech last month in which he expressed concern at the lengthy sentences.
Over the last decade his favourite dog, an adopted stray called Tongdaeng (Copper) which is praised for her loyalty and obedience, has been used to outline his vision of how Thais should behave.
An animated film about the dog last week shot to number two at box offices across the kingdom.
Most Thais have only known King Bhumibol as their monarch. Anxiety over the future once his six-decade reign ends is seen as an aggravating factor in Thailand's bitter political divide.