BANGKOK • Tens of thousands of tourists have fled some of Thailand's most popular islands as Tropical Storm Pabuk closes in and threatens to batter the southern part of the kingdom with heavy rains, winds and 7m-high waves.

Koh Phangan and Koh Tao, packed with holidaymakers during the peak Christmas and New Year season, have emptied out since Wednesday as tourists squeeze onto ferries bound for the southern Thai mainland, with swimming banned and boats set to suspend services.

Pabuk, Thailand's first tropical storm in the area outside of the monsoon season for around 30 years, is poised to hit the two islands as well as neighbouring Koh Samui this afternoon, before cutting into the mainland.

Packing winds of 104kmh, Pabuk is unlikely to intensify into a full-blown typhoon, according to forecasters.

"But we expect waves as high as 5m or 7m near the eye of the storm," said Thai Meteorological Department head Phuwieng Prakammaintara.

No official evacuation order has been given but tourists are leaving in droves, with those unable to book flights preparing to see out the storm on the eerily deserted islands.

"I think the islands are almost empty... Between 30,000 and 50,000 have left since the New Year's Eve countdown parties," Koh Phangan district chief Krikkrai Songthanee told Agence France-Presse.

The acting mayor of Koh Tao, one of South-east Asia's finest diving spots, said boats to Chumphon on the mainland were crammed with tourists, but several thousand guests were still on the island and likely to brave the storm.

"It's difficult to predict the severity of the storm so people should comply with the authorities' recommendations."

On Koh Samui, a Russian man drowned on Wednesday after his family ignored warnings not to go into the sea.

"A family of three went swimming but the strong current caught a 56-year-old man who drowned," Captain Boonnam Srinarat of Samui Police told AFP.

He added: "Island officials announced the warning and put up the red 'danger' flags... but maybe the family did not think the situation was that serious."

Bangkok Airways, which has a virtual monopoly on the air route to the island, cancelled all flights in and out of Samui today.

The authorities have prepared shelters for tourists who decided to wait out the storm or who could not secure seats on ferries for the mainland before services were suspended late yesterday.

AGENCE FRANCE-PRESSE