Klong Tan police investigator Lt-Colonel Parinya Wongkla said that after inquiries with the deceased's relatives, officers believed that severe stress led Boonchai Surawuthipong to murder his wife and three children before committing suicide. The family was found dead in their beds in their luxury Bangkok home on Tuesday.

"We are awaiting results of forensic tests for gunpowder on the deceased's hand and on the handwriting in the suicide note only to support our assumption," Parinya said yesterday.

He said neither Boonchai's relatives nor the man he had blamed in a suicide note were suspects.

Boonchai's suicide note claimed that a man he identified only as "Choosaeng" was going to harm his children if he did not pay him Bt5 million.

"We don't think the man is related to the murder-suicide. He told officers that he had avoided meeting anyone because he is afraid of the deceased's relatives, although the relatives told police they didn't know Choosaeng," Parinya said.

According to the officer, the relatives said Boonchai was a hard-working family man who always took things very seriously. They also believed the deaths were a case of murder-suicide triggered by stress from Boonchai's business, which was not going so well.