A French passenger was found dead on an Air France plane at Suvarnabhumi airport on Thursday morning.
Pol Col Montien Baothong, chief of Suvarnabhumi police, said the discovery was reported around 7am.
A 65-year-old man had been found dead on a seat on flight AF166 from Paris parked at Gate F6. There were no signs of injury on the body.
The man travelled to Thailand on a vacation with a friend. After the plane landed, his friend tried to wake him up so he could prepare to disembark. He instead discovered his friend was dead.
Police sent the body for a post-mortem examination at the Police General Hospital in Bangkok.
The man's name was withheld.