Nine provinces along Thailand's southern tail have been hit by unseasonal rains for nearly a week, with the resort islands of Samui and Phangan deluged, leaving thousands of tourists stranded or delayed.
Eight people have been killed and at least 120,000 households have been affected by the flooding across the south, the Interior Ministry said, where waters have turned roads into rivers and upended rail tracks.
Authorities fear worse may be to come.
The Thai Meteorological Department warned residents and visitors to the south of possible "heavy rain and flash floods" with downpours expected to continue for two more days.
Photos circulating on social media showed cars and motorcyclists plying through muddy, waist-high waters.
A smattering of foreign tourists on Samui took advantage of the flooded streets, drawing bemused looks from locals as they bobbed along in inflatable tubes sipping beers.
Tuula Fitzpatrick, the owner of Moby Dick guesthouse near Samui's main party strip, said the flooding was the worst to hit the island in over a decade.
"I've been living here for 12 years and I've never seen it so bad... It was scary. Some of my staff couldn't come to work," she told AFP.
The island, a stalwart of Thailand's cash-cow tourism industry, is a magnet for foreign visitors drawn by the promise of winter sun.
But under menacing skies tourists stayed inside hotels, while others checked out early or cancelled bookings, according to a Thai tourism official on the island.
