A recent assessment by Water Resources and Pollution Control officials found that Chai Nat's Thung Wat Sing and Sing Buri's Thung Chiang Rak were at the most imminent risk, Kasem said.

Ayutthaya's Thung Chao Chet, Thung Bang Pahan and Thung Makham Yong; Lop Buri's Thung Bang Kham; Nakhon Pathom's Thung Nakhon Chaisi; Angthong's Thung Phraya Banleau and Thung Pho Thong; and Chai Nat's Thung Saweangha, Thung Krathin and Thung Nang Seu-Huai Ngu would also become polluted unless water was drained soon, Kasem said.

Officials were assessing water quality in other areas and should be finished next week, he said.

Kasem said he had consulted the Royal Irrigation Department on which areas could drain polluted water into canals or rivers before November 15, while floodwater in other areas that had no canal connections would be pumped out.

Meanwhile, Phitsanulok public health officials sent a mobile lab to test food and drinking water quality at Bang Rakam markets and restaurants in a bid to prevent an outbreak of diarrhoea.

Flood damage forced 545 schools in 18 provinces to remain closed as the new term began yesterday. They are expected to open in two weeks.

The schools would have to make up classes on weekends, holidays and longer days to help students catch up on missed lessons, said Kasama Varavarn na Ayutthaya, the secretary-general of the Basic Education Commission.

The cost of damage from the flooding was initially estimated at Bt800 million but several submerged schools could not be repaired at present, she said.

Agriculture and Cooperatives Minister Thira Sutabutra said he told the Cabinet meeting on Tuesday that compensation to be paid to farmers for flood damage would be Bt2 billion.

The floods damaged 5.9 million rai of farmland in 60 provinces, killed 3.4 million head of livestock in 35 provinces, and damaged 122,562 rai of fishery areas.

Disaster Prevention and Mitigation Department chief Anucha Mokhawet said the estimated losses had reached Bt448.2 million.

The floods affected almost four million people in 47 provinces, with 170 deaths reported. Parts of 15 provinces are still submerged.

In related news, HRH Princess Srirasmi, the Royal Consort of HRH Crown Prince Maha Vajiralongkorn, assigned representatives to visit flood-affected residents in Tambon Bang Chao Cha in Angthong's Pho Thong district and ensure cooks at the Princess's "Krau Saiyai Rak" mobile kitchen made enough food for thorough distribution. The kitchen will be expanded to other provinces also.