A hero motorist alerted a bus driver about fire engulfing the back of the vehicle and helped put it out.

Sakhon Ritthitit noticed flames building up in the compartment of a public utility bus, so he accelerated his car to catch up to it and inform the driver about it in Ubon Ratchathani province, Thailand, on April 1.

Footage shows Sakhon increasing his speed, signalling to the bus driver from his window, and honking to get his attention.

The bus then stopped and they were able to control the blaze before it could spread to the passenger seat above.

Sakhon said: 'It happened very quickly. The flames started to flicker and grew, so I had to catch up to the bus to let the driver know.'

The bus operator Transport Company Limited later said that the cause of the fire was the electrical wire in the engine compartment repeatedly touching the metal cage, creating sparks.

After the incident, the driver wrapped the wire with tape before transporting his 40 passengers to Ubon Ratchathani Bus Terminal, approximately 60 kilometres from the scene.

The trip was delayed for an hour as the driver had to travel cautiously, but no one was hurt by the fire.

The bus was taken for repair and resumed operation.