This is the moment a Thai man knocks out an Australian pensioner with a vicious punch in a road rage argument.

Expat Colin Gerrard, 72, had been collecting his eight-year-old daughter from school in the afternoon of October 11 in Pattaya, Thailand.

He claims that he indicated to turn right but local driver Sumet Rungratanapan, 28, tried to overtake as he pulled out - causing a minor scrape.

The two men then squared up in the middle of the street when Colin produced a machete from inside his car, which he admitted to and was pictured on his front seat, and allegedly smashed the Thai man's car window.

The dispute is filmed as each party tells officers and reporters their version of events.

Then with a traffic policeman standing between them, they then carry on arguing with enraged Sumet yelling 'I have a clip' as his wife stands next to him saying 'how dare you'.

But Sumet then unexpectedly takes a run-up and throws a powerful left hook - instantly knocking out Colin who falls backwards onto the ground.

The Australian was out cold for around a minute then came round in a daze with blood pouring from his left eye and onto his shirt as his daughter stands crying.

The entire punch-up was filmed by a reporter who attended the initial traffic dispute.

Sumet, who runs a shop selling gold jewellery, said: ''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.

''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 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.''

Filmed by a reporter, Colin is heard admitting he was brandishing the large jungle knife.

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

Colin received first aid treatment at the roadside for a cut to the left side of his face.

Officers calmed the situation and both men were ordered to attend Pattaya City Police Station today to be questioned over the incident.

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.''