Two people remained missing out of the 30 aboard the boat, on a diving cruise, that sank early Monday about 19 kilometres off the coast of Phang Nga province.

"We found the wreckage of the vessel at the bottom of the sea, about 60 metres to 70 metres deep," said marine police Colonel Wanlop Puangpaka. "Four bodies were stuck inside."

Twenty-three people were rescued from the sea a few hours after the boat sank, marine police officer Parinya Kaewplung said.

A body retrieved Tuesday was identified as Gabriele Jetzinger, 51, from Austria.

Police believe the bodies found Wednesday are those of an Austrian, a German and two Swiss nationals.

Wanlop said the search would continue Thursday for a Japanese tourist and a Thai national, the boat’s cook, who are still unaccounted for.

The cause of the accident was still being investigated.

Boating accidents in Thailand are often caused by rough seas during the monsoon season, overcrowding or poorly enforced safety standards. The sea was calm before Monday’s accident, Parinya said.

The boat was returning from the Similan islands, 120 kilometres northwest of Phuket, one of Thailand’s top tourist destinations.

AP / Expatica