Twelve provinces in the North and the Northeast have been told to prepare for heavy rain starting on Monday as Typhoon Yagi makes landfall in Vietnam on Saturday.
According to the National Hydroinformatics Data Center (NHC), the typhoon is expected to be downgraded to a low-pressure area as it moves inland over the upper part of Laos.
Beginning on Saturday, heavy rain will fall on the northern provinces of Mae Hong Son, Chiang Mai, Tak, Chiang Rai, Lampang, Lamphun, Phayao, and Nan and the northeastern provinces of Loei, Nong Khai, Bung Kan and Nakhon Phanom.
The Meteorological Department has also urged those in the eastern region and the western part of the South to brace for heavy rain and possible flash floods due to the influence of the southwestern monsoon.
Waves in the Andaman Sea and the upper part of the Gulf of Thailand are forecast to swell to three metres high, while small boats are advised to remain on shore this weekend.
Surasee Kittimonthon, secretary-general of the Office of the National Water Resources (ONWR), said water reception areas have been prepared to decrease the volume of water flowing into Chao Phraya dam in Chai Nat, which is the main regulator of water from the North.
He said the water passing through the C2 water station in Nakhon Sawan is expected to increase by 1,500-2,000 cubic metres per second during Sept 9-10.
Mr Surasee added that all parties concerned have been asked to draw up plans to prevent and mitigate flooding and a forward command centre will be set up on Sept 15 in Ayutthaya to manage the water situation in the Central Plains.