Northern Thailand was placed on alert as flash floods submerged farmland and homes.

The region was battered by continuous heavy rain on Tuesday, triggering severe flooding in eight districts of Chiang Mai province near the border with China.

Footage shows villagers placing sandbags on the street to shield their houses from incoming mountain runoff.

Authorities said the Chiang Dao district was the hardest hit, recording 102 millimetres (four inches) of rainfall overnight. The floods spilled over into low-lying areas, engulfing homes, rice paddies, farmland, and roads in their path.

Emergency crews scrambled to evacuate residents along the swollen Ping River.

The downpour has today subsided as district officials began assessing the damage. They said the water level at the Nawarat Bridge was at 5.2 ft (1.6 metres), well below the crisis level of 12 ft (3.7 metres). However, warnings were still raised for high-risk areas to be vigilant of heavy rain, flash floods, and landslides.

The Northern Meteorological Centre reported that the region was being lashed by torrential rains due to the combination of a low-pressure cell covering Laos and northern Vietnam, and the strong southwesterly monsoon prevailing over the Andaman Sea and the Gulf of Thailand.

Thunderstorms were expected to affect 80 per cent of northern Thailand, with heavy to very heavy rain in some provinces, including Chiang Mai, the agency said.

Thailand and neighbouring countries in Southeast Asia are in their annual monsoon rainy season which sees soaring temperatures followed by powerful rain storms in the afternoon leading to widespread flash floods.