According to police, circumstantial evidence pointed to suicide, reports the Bangkok Post.
Police made the remarks after a user of the Facebook account named Koh Tao Death Island posted videos about the death of the Japanese scuba instructor.
The user posted that Yoshie ‘Sharlyn’ Sazawa died in suspicious circumstances but local police dismissed her death as a suicide despite the absence of any suicide note.
However, Pol Maj Gen Sathit Pholphinit, chief of Surat Thani Provincial Police, said an investigation by Koh Tao police in Koh Pha-ngan district concluded the Japanese diving instructor died in 2004, but was not murdered.
She was a tourist visiting Koh Tao and rented a house on the hill near Moo 2 of Ban Mae Hat in Tambon Koh Tao, Pol Maj Gen Sathit said.
She was later found dead in the house.
An investigation turned up no evidence that she was killed by any other person.
At the scene, a letter was also found with a message written by her as a farewell to her relatives, Maj Gen Sathit said.
After an autopsy was conducted on the body, the case was presumed to be a suicide and her relatives agreed to lay to rest any lingering doubts about the cause of her death, he said.
Koh Pha-ngan District Chief Poonsak Sophonpatumrat said the Koh Tao Death Island Facebook page belonged to a group of foreigners whose motive is to revive and dig up incidents that happened on Koh Tao in the past.