An elderly lady and her grandson were knocked off their bike by a reckless van driver who sped away from the accident.

Dashcam footage from the motorist driving behind them captured the shocking moment they were nudged off balance by the vehicle on their right in Nakhon Ratchasima, north eastern Thailand on June 8.

The young lad was able to stand up after falling and rushed to help his grandmother lying on the ground.

The van driver slowed down his vehicle to take a look at the injured relatives but did not stop and continued driving away from the scene.

The pair were taken to a nearby hospital by paramedics to treat the old lady, who suffered a broken arm, while the boy suffered minor scratches and bruises.

Police said they would trace driver to question them and request they pay for the damages.