Flooding has caused chaos in parts of southern Thailand and north Malaysia, making some areas inaccessible.
In the Thai city of Hat Yai cars were submerged, power supplies were interrupted and transport links cut.
In northern Malaysia, 28,000 people have been displaced and an airport closed because of a flooded runway.
The flooding follows days of heavy rain in the region. More than 100 people were killed by floods in northern Thailand in October.
The latest flooding affected Hat Yai, the commercial capital of southern Thailand.
In some places water levels were said to have reached 3m (10ft), and many roads were under water.
The Thai government has sent soldiers and its only aircraft carrier to the area to help local residents.
The vessel, now anchored off Hat Yai, has helicopters, landing craft and relief supplies to distribute.
In Malaysia, meanwhile, tens of thousands of people have been evacuated in two northern states, Perlis and Kedah.
Perlis chief minister Mohamad Isa Sabu said the floods were "really bad".
Local media said one person had been killed and another was missing in Kedah, where an airport was closed.
The Thai authorities also closed an airport on the popular holiday island of Ko Samui on Tuesday but officials said it would reopen on Wednesday.