The body of the white woman, described by police as European, was found 20 kilometres off the resort island of Phuket.

It came as 30 marine police and volunteers searched for six foreigners and one Thai whose boat overturned in a storm on Sunday.

"The rescue team found the body of a European female floating near the accident site," Lieutenant Colonel Wallop Puangpaka of Phuket marine police told AFP.

"But we cannot be sure that she was one of the six tourists. We have to wait for a doctor’s autopsy," he said, adding that the body was being transported to the hospital in the town of Phuket.

The boat, carrying 30 people including 19 foreigners, was reported missing at 16h00 GMT on Sunday. It sank in stormy weather on its return from the Similan islands off southern Thailand.

Police and navy rescued 23 passengers and crew on Monday afternoon but two Swiss nationals, two Austrians, a Japanese, a German and a Thai member of the crew remain missing.

A senior official, who declined to be named, said the chance of the seven surviving was now slim as he suspected they were trapped inside the overturned 18-metre boat.

A helicopter failed to spot the seven divers on Monday despite calm waters, he said.

"Now we are looking for specially-trained divers who can dive down to (the boat)," he added.

Phuket, Thailand’s biggest island, is one of the kingdom’s leading tourist draws, with holidaymakers attracted by its beaches, resorts and spas, and seas popular with divers.

AFP / Expatica