A three-day search found no sign of a Russian woman missing from a beach since Oct 20 and she is believed to have drowned.
Elena Rusradchenko, 53, was last seen at Nai Thon beach in Thalang district on Thursday. Police were informed of her disappearance on Friday.
Bancha Thanu-in, the Thalang district chief, said a search centre was set up at Nai Thon beach. More than 100 people were involved in the search, which began on Friday night by land, sea and air.
Searchers scoured Nai Thon beach, a line of rock formations along the beach, construction camps, an elephant kraal and the forest. Rubber boats were used to search in the sea along the shore. A helicopter from the 3rd Naval Area was provided for an aerial search.
After three days, the search had failed to find her.
On Sunday at 6pm, provincial governor Narong Woonciew chaired a meeting where he was briefed on the search. Afterwards, Mr Narong said the Russian tourist was believed lost in the sea.
He said the Russian consulate in Phuket and the Russian embassy in Bangkok had been informed. The search would continue on Monday over a wider area.
Friends of the missing woman offered a reward of US$10,000 to anyone who had information on her whereabouts and reported it to Sakhu police station, Mr Narong said.
Pol Col Pichetpong Chaengkhaikhom, the Phuket tourist police chief, said the missing woman arrived with a group of friends on Oct 16. They stayed at a hotel at Nai Thon beach. The group was scheduled to fly home on Oct 29.