Chatchai Phromlert, director-general of the Department of Disaster Prevention and Mitigation, said the rain-fuelled flooding from the North was expanding in Sukhothai and had started to affect Phitsanulok province.
Runoff had raised the level of the Chao Phraya River and its tributaries by 1-2 metres and that could cause sudden flooding in riverside and low-lying areas.
Darongkorn Somton, director of Regional Irrigation Office 12 in Chai Nat province, warned that rivers could overflow in Chai Nat, Uthai Thani, Sing Buri, Ang Thong, Suphan Buri, Ayutthaya and Lop Buri provinces, all in the Chao Praya river basin, because the Chao Phraya dam in Sapphaya district of Chai Nat had to increase its discharge rate due to excessive inflow of water from the North.
He said that flooding would start to affect riverside areas in Bang Luang Dote sub-district of Bang Ban district and Ban Krathum and Hua Wiang sub-districts of Sena district in Ayutthaya.
The Noi River started to overflow and swamped about 100 riverside houses in Hua Wiang, Ban Krathum, Ban Pho and Ban Phan sub-districts of Sena district. Increased discharges from the Chao Phraya dam in the Chao Phraya River could spread the flooding to about 1,000 houses in the four sub-districts next week, because the Chao Phraya and Noi rivers are connected, local authorities said.
Meanwhile, floodwater from Sukhothai was flowing to Phrom Phiram and Bang Rakam districts of Phitsanulok province.
Bundit Inta, irrigation director of Phitsanulok, said that Phrom Phiram and Bang Rakam districts were receiving floodwater from both Sukhothai and Phrae provinces and flood levels in both districts should be rising on Sept 6 and 7.
Flooding started in Tha Chang sub-district of Phrom Phiram and Chumsaeng Songkhram and Bang Rakam sub-districts of Bang Rakam. They are low-lying areas and some local paddy fields have not yet been harvested.
In Sukhothai, flooded districts were identified on Friday as Si Satchanalai, Sawankhalok, Kong Krailat, Muang Sukhothai and Si Samrong.
Col Sirijan Ngathong, deputy spokesperson of the Army, said floods already disappeared from the upper North and the inundation in Sukhothai would expand over the next few days due to water from Phrae province.
She said Si Nakhon and Thung Saliam districts of Sukhothai were also flooded. About 4.5 square kilometres of farmland in Sukhothai were under water.