Bangkok (CNN) Thousands of people are fleeing Thai islands popular with tourists ahead of what could be the most devastating storm to hit in decades, officials told CNN on Thursday.

Tropical Storm Pabuk is expected to make landfall about 7 p.m. local time Friday (5 a.m. ET) near the Chumphon archipelago, on the eastern border of Thailand's Surat Thani and Nakhon Si Thammarat provinces, but heavy rain has already arrived.

Tourist hotspots in the Gulf of Thailand, including Koh Samui, Koh Phangan and Koh Tao islands, along with islands in the Andaman Sea such as Phuket and Koh Phi Phi -- made famous by the movie "The Beach" -- are expected to be affected by the storm.

"We are still compiling the number of evacuees. I can say several thousand people for over 16 provinces," government spokesman Putthipong Punnakanta told CNN by phone.

"It is high season, there are many foreign tourists at popular destinations. We have informed them in advance since two days ago. I would say most of them have left islands and come to the mainland."

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