Human remains believed to be those of a missing Russian tourist have been found in a forest on a Thai island.

The body was discovered by a Burmese national who was exploring the woods on Koh Pha Ngan, Surat Thani province, on October 12.

The corpse was identified as Nikita Gragorep, 30, a Russian patient who was being treated at the Pha Ngan Hospital around a mile away from the forest.

CCTV shows Nikita' leaving the facility on September 13, with his friends filing a missing persons report and asking for help on social media as they claimed Nikita was suffering 'acute psychosis'.

They also promised a reward of 35,500 THB (around 930 USD) but no one could point to the tourist's whereabouts.

The cadaver was found on October 13 still wearing an orange tank top and plaid shorts - the same outfit Nikita was wearing when he was last seen.

Officers said the body showed no signs of struggle or physical harm, adding the deceased may have died from dehydration.

Nikita's friends have reportedly confirmed his identity, but an official DNA test is still pending.

Police Colonel Panya Nirattimanon, superintendent of the Koh Pha Ngan police station, said: 'Police have visited the area to examine the scene thoroughly and determine the cause of death.

'The case has been reported to the Russian embassy, but we are still collecting evidence to clarify the details.'