A 58-year-old Finnish man was found dead on his bed with his throat cut and a knife on his chest at his home in Chon Buri on Tuesday morning.
Police were questioning his Thai wife, who said she found him dead after taking a young relative to school.
Local police found the dead man lying on a bed, wearing only a pair of underpants.
His neck was cut. A kitchen knife was lying on his chest. His 49-year-old wife was sitting in the room, crying.
She said they had lived together for about five years.
Her husband had returned to Finland and stayed there for about two years. He arrived back in Thailand about nine months ago and bought the house.
On Tuesday the man woke up about 6am. She prepared a meal and coffee for him and left to take her young relative to school.
When she returned home, the house was quiet. She then saw blood in the room and found her husband's dead body, his throat cut and a knife on his chest.
She said the man had taked about committing suicide several times, because of domestic problems in Finland.
The man's body was taken to Police General Hospital in Bangkok for autopsy.
Police were questioning the woman further about the man's death. Neighbours told police the couple often argued.