The missing tourist, Maksim Shchartsou, was last seen playing in the water at the southern end of the beach at dusk.
Capt Akkarapon Siwilai of the Sakoo Police said he was notified that Mr Shchartsou was missing at 7pm.
Mr Shchartsou arrived in Thailand with female compatriot Irene Roslik , 29, only yesterday, Capt Akkarapon reported.
The couple had checked in at a nearby resort located further south.
Police were told that Ms Roslik stayed on the beach while Mr Shchartsou continued to play in the water for a long time.
Only later did, Ms Roslik notice that Mr Shchartsou was missing and raised the alarm.
The area where Mr Shchartsou was swimming is not patrolled by lifeguards.
A search for Mr Shchartsou was launched last night, but failed to find him.
The search was called off late last night after conditions made it dangerous for the search teams.
The search continues today.
The search for Mr Shchartsou off Nai Thon beach today comes as the search continues for local resident Sarawaut Dungsikaew, 38, who disappeared at Layan Beach while fishing for crabs on Tuesday evening (Oct 29). (See story here.)