Joined by onlookers, he made an impromptu picnic on Wednesday night outside the Thai police headquarters as protesters splashed it with paint and sprayed graffiti nearby.
“For those who are still at home, did not join the protest and think that there is violence or that we are using violence on the authorities, I want to show them there is no violence,” the man, who gave his name only as Mew, told Reuters.
The demonstration followed the most violent day in months of protests, when dozens were hurt as police used tear gas and water cannons to try to push back protesters.
Prime Minister Prayuth Chan-ocha said on Thursday that all laws would be used against protesters who break them.
The protests seek his removal, a new constitution and reforms to the powerful monarchy.