Wilson, who starred in "Midnight in Paris", and former James Bond Brosnan had just finished Wednesday's shoot for the action-thriller "The Coup" when the fire broke out in a three-storey shophouse being rented for the film in the town of Lampang.
"Neither Owen Wilson nor Pierce Brosnan or (co-star) Lake Bell were anywhere near the set when the fire broke out... it was after wrap so none of our actors were there," said Chris Lowenstein of production company Living Film, which is helping the shoot.
"No-one was injured in the fire" which broke out in the ceiling, he added.
The scene had involved "air mortars with dust, cork and debris" but not "explosions, fire or other pyrotechnics", he said.
Local police said the fire is suspected to have started after special effects were used in the shoot.
"Forensic police are examining the place to find the actual cause," according to Police Colonel Thanakorn Khumwong.
The plot of "The Coup" pivots on an American family trapped in a Southeast Asian country in the middle of a military uprising.
Thailand has experienced nearly 20 military coups or attempted coups since it became a constitutional monarchy in 1932. AFP