"Alongside our warnings about possible flash-floods and landslides, we instructed the village head to evacuate all residents," said Weerawut Pornratpan, hydrology director of the Water Resource Region 1 Office.

Everyone in Ban Sukrutai in Mae Ai district was evacuated to a school on higher ground after rainfall between 5.15am and 7.45am was measured at 101 millimetres.

By 10am, the amount of rainfall had risen to 145 millimetres.

A flash-flood then swept through the village and inundated several houses.

About 10 pigs were swept away, and a survey was being conducted to determine damage to roads and other infrastructure.

As many as 10 houses were buried under landslides. There were no reports of casualties.

Mae Ai district chief Niwes Poonsawas said there were 33 "risky" villages in his district. "We are closely monitoring the situation, especially in high-risk areas," he added.

Normally, flood warnings are issued when rainfall reaches 200 millimetres in a 24-hour period.

Weerawut, however, said the intense rain in just a few hours had pushed the accumulated rainfall to 101 millimetres and he alerted authorities.

In Chiang Mai's Mae Chaem district, a survey showed floods on Sunday night damaged up to 60 houses, 47 bridges and 400 rai of farmland.

Meanwhile, Deputy Bang-kok Governor Bannasophit Mekwichai said the capital looked set to see a 30-per-cent increase in rainfall.

"Rainfall usually stands at about 1,500 millimetres a year on average, but this year we believe Bangkok will receive 1,800 to 1,900 millimetres," she said.

Bannasophit said the situation could be most worrying in October.

As a preparation, she said Bangkok Metropolitan Administration now had up to four million sandbags ready and had dredged up to 102 canals.

"We have also released some water from canals and retention areas," Bannasophit said.