This is the dramatic moment a bridge collapsed amid floods caused by heavy rain in Thailand.

The Wang Sakaeng Bridge in Chiang Mai province had been in disrepair since October last year, and finally collapsed following monsoon storms on September 30.

Footage shows how the structure spanning the Ping River crumbled into the stream, sending large waves toward onlookers on the river bank.

Authorities have last year banned heavy vehicles from using the bridge, which connects Chiang Mai and Lamphun provinces, due to subsidence. However, villagers allegedly continued driving over it on bikes or motorcycles.

Local media reported that residents felt 'relieved' at the collapse due to the bridge's dilapidated state. Motorists have been advised to use a different bridge some 10 kilometres away as an alternative route.

The incident caused no injuries and has been reported to Chiang Mai governor Nirat Pongsittithavorn.

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.