He was arrested by immigration police and returned to Koh Chang for a brief detention, but is now out on bail.
Barnes, who works in Thailand, had penned multiple reviews on different sites over the past few weeks, the hotel alleges.
In one posted in July, he claimed to have encountered "unfriendly staff" who "act like they don't want anyone here".
Another post, which accused the hotel of "modern day slavery", was removed by TripAdvisor for violating its guidelines.
The Sea View Hotel said they only took legal action to discourage further reviews from being posted, and had attempted to contact Barnes beforehand.
"We chose to file a complaint to serve as a deterrent, as we understood he may continue to write negative reviews week after week for the foreseeable future," the hotel said.
Thailand has notorious anti-defamation laws that have faced condemnation from human rights organisations in the past. They argue the laws can be used to stifle free expression.
If found guilty for defamation, offenders can face two years imprisonment and a 200,000 baht (NZ$9655) fine.
In December 2019, a Thai journalist was handed a two-year sentence for libelling a chicken farm on Twitter.
Suchanee Cloitre was convicted for a post she made about a legal dispute over working conditions at the Thammakaset farm.
"I'm shocked and did not think the sentence would be so harsh," Suchanee told Reuters after the sentencing.
- The Telegraph UK
