Thai Airways International has apologised for an incident where hot coffee was spilled on a passenger, causing serious burns.

The airline said on Sunday it felt truly sorry for the incident and promised compensation for the injured passenger. It also said that the airline management was investigating the issue.

The airline's apology followed a complaint from the injured passenger that a flight attendant dropped a cup of hot coffee while reaching across to serve another passenger in the same row of seats. The cup was served by hand instead of being placed on a tray as usual, according to the complainant.

The injured passenger on a recent Chiang Mai-bound flight from Bangkok claimed he suffered severe burns over many areas of his body and had to receive treatment at hospital.

The passenger said that the flight attendant failed to give him first aid in a professional manner.

The attendant only sent him to a wheelchair pusher at Chiang Mai airport before leaving him. He said the adjacent passenger who ordered the cup of hot coffee apologised to him repeatedly, went with him in an ambulance to hospital and waited until he was discharged from an emergency room.