At least four people were killed as floods displaced thousands from their homes in northern Thailand.

Severe flooding caused by seasonal rains has wiped out more than 5,000 acres of farmland and submerged at least 5,579 houses in Chiang Rai province since August 16.

Authorities said four villagers, including a 77-year-old angler who drowned while fishing in a flooded rice field, were killed by the deluge. Some locals were found by rescue teams trapped on the roofs of their houses to escape the rising waters.

Chiang Rai Deputy Governor Prasert Jittpleecheep led relevant agencies in surveying the damages and handing out relief goods to residents.

The Provincial Disaster Prevention and Mitigation Office said that the flooding had also knocked down power and triggered landslides across the province.

Police Colonel Pornsak Laorujiralai, acting commander of the Marine Police Division, said police units have been dispatched on boats to provide aid in flood-stricken areas.

The Thai Meteorological Department warned that widespread thunderstorms and heavy rain will continue to batter northern Thailand on August 22.

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.