Confronting footage has emerged of the moment an Australian pensioner is knocked out with a sickening coward punch.

Colin Gerrard, 72, was involved in a traffic dispute with a local man outside his daughter's school in Pattaya, Thailand at 4pm on Wednesday.

As the two spoke to a police officer the Thai man appeared to be walking away before suddenly turning around and hitting the elderly man with a powerful blow.

The unexpected punch left Mr Gerrard out cold for about one minute before he came to on the ground, blood pouring from a gash in his face.

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Confronting footage has emerged of the moment an Australian pensioner (pictured, left) is knocked out with a sickening coward punch

Colin Gerrard (pictured, left), 72, was involved in a traffic dispute with a local man outside his daughter's school in Pattaya, Thailand at 4pm on Wednesday

The attacker, 28-year-old Sumet Rungratanapan, runs a jewellery store and was wearing a large gold ring when he hit Mr Gerrard.

The pair were involved in a minor traffic accident before Mr Gerrard took a machete from his car and smashed the windows of the Thai man's vehicle.

'I was driving my car and I wanted to overtake but the foreigner didn't want me to go in front of him. He moved the car in front of me,' Mr Rungratanapan said.

''After that I said sorry because I scratched his car but then the foreigner was shouting and swearing at me. It made me angry and I started to talk bad back to him.

The pair were involved in a minor traffic accident before Mr Gerrard took a machete (pictured) from his car and smashed the windows of the Thai man's vehicle

'Then I walked over to him and he took the knife and he attacked my car (pictured) with it. I was so angry and I just punched him,' said the Thai man

'The foreigner was shouting to stop the car and come outside. Why was he talking to me, a young person, saying come here, come here, so strongly?

'Then I walked over to him and he took the knife and he attacked my car with it. I was so angry and I just punched him.'

Mr Gerrard can be heard in the video telling the officer he used the machete.

'I bash[ed] his car,' he tells the officer.

'Basically I held the knife to stop him. I said "stop, stop". He attacked me.'

Moments before the punch Mr Rungratanapan says 'I have [a] clip' and appears to watch footage of Mr Gerrard smashing his car before losing his temper.

Mr Gerrard (pictured) can be heard in the video telling the officer he used the machete

A woman holding a child and filming the encounter - believed to be Mr Rungratanapan's wife - says 'How dare you? You cannot use [a] knife.'

The Australian was treated for a cut to the left side of his face, and both men attended Pattaya City Police Station on Thursday for questioning.

Police Lieutenant Colonel Nakhonrat Nonsilad, deputy leader of investigations, said: 'We have to hear both sides of the story and the injured man must get a medical certificate from the hospital as evidence of his injuries.

'Neither man has been charged. We have to wait for the interrogation of all parties, interviews with witnesses and check CCTV footage.'