Ukraine's ambassador to Thailand died early Sunday on the southern beach island of Koh Lipe while on vacation with his son, police said, with the cause of death still undetermined.

Andrii Beshta is a 45-year-old career diplomat who was appointed as Ukraine's ambassador in Thailand in 2016.

The National Police said Sunday Beshta was found dead around 5:30 am (2230 GMT) in his room at a hotel resort in Koh Lipe, an idyllic beach island popular with travellers for its crystal-blue waters.

"Preliminary investigations showed no signs of him being attacked, no signs of a raid or violence," said a statement attributed to National Police deputy spokesman Kissana Phathanacharoen.

The medical team first on the scene had wore PPE suits as a precaution to investigate the body, while authorities had questioned the ambassador's son Ostap, who had shared the room with him.

He said his father had gone to bed around 11 pm the night before, but had woken up at 4:30 am vomiting before falling unconscious, said Kissana, who added that other witnesses were also questioned.

Beshta's body was sent first to a local hospital for an autopsy, before it was transported to a police hospital in the Thai capital Bangkok for further investigation into his cause of death.

He has spent more than a decade of his career in Thailand, according to the embassy's website, arriving first in 2007 as a counsellor to the diplomatic mission in Bangkok.

He was appointed the embassy's deputy director-general in 2011, taking over as ambassador in 2016.