A witness told police that the car had been parked in the same place since midday. A local person riding by on his motorbike stopped to check when he saw Mr Phumin slumped inside, with the door unlocked.
Neighbours noted that Mr Phumin had recently had family problems that had led him to heavy drinking.
Police theorised that Mr Phumin had decided to sleep in the car, with the engine running and the air-conditioning turned on. When the engine stopped, however, he suffocated. Or, possibly, he had decided to commit suicide by suffocation.
The truth is unlikely to be known as the family of the dead man declined an autopsy, instead asking that his body be sent to his home town for cremation.