Singapore Airlines flight SQ321 took off from London Heathrow last night, but was diverted to Bangkok where it landed this afternoon, local time.
One person on board died, and another 30 people were injured, Singapore Airlines said.
There were 211 passengers and 18 crew on board.
“We can confirm that there are injuries and one fatality on board the Boeing 777-300ER,” the airline said.
“Singapore Airlines offers its deepest condolences to the family of the deceased.
“Our priority is to provide all possible assistance to all passengers and crew on board the aircraft.”
The plane landed at 15.45 local time.
The airline said it is working with Thai authorities to get medical help.