Rainfall is expected to be moderate in the South, on both the Andaman Sea and Gulf of Thailand sides, today and tomorrow, but isolated thunderstorms remain a threat, the department said.
Rainfall is likely to intensify, especially in the South, from Tuesday, it said.
Today and tomorrow it will be heaviest in the East and Central regions, including Bangkok, as well as in provinces in the northwest, the department said.
A high pressure system over the upper Northeast will keep rainfall there to a minimum, with light to moderate rainfall expected in the late afternoon or evenings.
In the South, rain will increase over the week ahead, especially in Krabi, Phang Nga, Phuket, and Ranong provinces. Waves could exceed two metres in height in the Andaman Sea in the week ahead, the department said, urging fishermen to remain vigilant before heading out to sea.