Thai authorities on Friday warned of flash floods across the south as torrential rains lashed the region leaving at least six people dead, delaying flights and disrupting holidays during peak tourist season.

Nine provinces along Thailand's southern tail have been hit by unseasonal rains for nearly a week, with the resort islands of Koh Samui and Koh Phangan deluged, leaving thousands of tourists stranded or delayed.

Six people have been killed and at least 120,000 households have been affected by the flooding across the south, the Interior Ministry said in a statement, where waters have turned roads into rivers and upended rail tracks.