It explained that the temperature will be dropping thanks to a strong high-pressure system from China that will cover upper Thailand and South China.
Apart from lower temperatures, the westerly wind will also hit the North and bring light rain to some areas.
Meanwhile, the Northeast monsoon over the Gulf of Thailand and the South is also strengthening, creating 2- to 3-metre-high waves in the lower Gulf of Thailand that become even higher in thundershowers.
Very high waves can also be expected in the upper Gulf of Thailand and the Andaman Sea.
From Tuesday to Thursday, the moderate high-pressure system covering the upper Northeast and South China Sea will weaken, and though it should get warmer in the upper parts of the country, the weather will still be cool with light fog.
The westerly wind will continue covering the North with isolated light rain.
The Northeast monsoon over the Gulf of Thailand and the South will create up to 2-metre-high waves in the Gulf and the Andaman Sea.
TMD has urged people in upper Thailand to look after their health, and people on the East coast in southern Thailand to beware of choppy seas.
It also said ships in the Gulf of Thailand and the Andaman Sea should proceed with caution throughout the period, while small boats in the lower Gulf should keep ashore from Saturday to Thursday.
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