A Russian tourist on a birthday holiday has gone missing while swimming in choppy seas on the Thai island of Phuket.

Elena Radchenko, 53, was on a trip with friends when she walked out from her hotel to the region's Nai Thon beach on October 20.

Locals said Elena and other beachgoers were warned against entering the water due to the seasonal currents, which are particularly strong in southern Thailand between October and January.

Elena reportedly walked back to the shore, but instead of returning to the hotel, she 'went the other way' while looking 'absent-minded,' a beach guard claimed.

She left her towel, sandals and bottle of water on nearby rocks before going into the sea but disappeared amid the waves.

A search and rescue operation involving dozens of personnel was launched the following day after a missing person report was filed on October 21.

Rescue teams scoured both land and sea for traces of the missing tourist, who is said to be a senior executive of a company in Russia.

As of October 24 - the fourth day of searching - officials are yet to find any trace of Elena.

Trin Panyawai, president of the Sakhu Tambon Administrative Organisation, said: 'We are continuing our search and expanding the search area, but we are not ruling out any possibilities.

'The provincial and district police are working together. No issues have been ruled out yet.'

Police Colonel Pichetpong Chaengkhaikhom said Elena arrived with a group of friends on October 16 and they were scheduled to depart on October 29.

He added: 'This is a dangerous time of the year to swim in the sea. Tourists are advised against swimming.

'There are red flags on the beach to warn people that the sea is dangerous now.'

Friends have now offered a 10,000 USD reward for any information which helps to find Elena.