In Trang province, about 1,000 households in three districts - the provincial seat, Huay Yod and Kantang - were flooded by the Trang River which overflowed its banks.
Some 10,000 rai of farmland including rubber and palm oil plantations, were under floodwater, with estimated damage around Bt10 million.
In Songkhla, a flash flood hit Songkhla municipality, especially areas near Songkhla Lake. Roads and homes were under 50-centimetre deep floodwater due to high tide and slow water drainage.
Songkhla municipality is speeding up water drainage operations.
In the restive southern province of Narathiwat, forest runoff from the Sankalakhiri mountain range from continued heavy rain overflowed the Sungai Kolok and Bang Nara rivers.
Six low-lying and riverside communities in Sungai Kolok municipality were inundated.
One hundred twenty households were affected, forcing 137 persons to evacuate to temporary shelters.
Heavy downpours also triggered floods in three other districts - Wang, Rangae and Ruso.
The weather agency reported today that the strong northeast monsoon across the Gulf of Thailand and the South and the low pressure area over the Malaysian coast will lead to isolated heavy to very heavy rain over Nakhon Si Thammarat, Songkhla, Pattani, Yala, Narathiwat, Trang and Satun.
People should beware of the severe weather. Strong winds will produce 2-3 metre waves in the Gulf. All ships should proceed with caution and small boats in the Gulf of Thailand from Nakhon Si Thammarat southward should keep ashore.