A man from Finland was found dead in a house in Bang Lamung district by neighbours late on Sunday night.
Police and a rescue team were called to a house at Pattaya Rung Ruang housing estate in tambon Nong Prue about 11.30pm.
They found a naked man lying dead on the bedroom floor. He was believed to have died several days earlier, based on the condition of the body. There were no traces of physical violence. The house had not been ransacked.
The man was identified as Tim Jhani Muhonen, 54, from Finland.
The neighbours who called police said they had noticed a foul smell coming from the house for a few days. The smell had become so strong they had trouble sleeping on Sunday.
They said five or six days earlier a Thai woman came to visit the man. Before she left, she was overheard telling the man not to lock the door.
Police were investigating.