A report by Koh Lipe Police Station said that the ambassador had possibly died due to acute heart failure.
Police said there was no evidence of pain or injuries on his body or signs of foul play at the scene.
Ostap Beshta, the 17-year-old son of the ambassador, said his father was in the room at 11pm on Saturday before he vomited and lost consciousness at 4.30am.
Police and Koh Lipe Tambon Hospital will continue to investigate the cause of death, Koh Lipe Police Station investigation officer Pol Captain Beedan Saripa said.
Beshta was appointed as Ukraine’s ambassador to Thailand in 2015 and came to the country in 2016. He planned to return to Ukraine later this year.
The Thai Foreign Affairs Ministry said the Department of European Affairs was cooperating with the Department of Protocol on issues related to the ambassador’s death.