This is the dramatic moment three prisoners escape after a bungling guard left a prison truck's engine running with the key in the ignition.

The white van arrived at a court in Chumphon province, southern Thailand at 8.55am with ten suspects inside due to stand trial.

But the as the blundering guard went to open the rear cage for the men, two of them ran outside in a bid for freedom. One made it onto the road while another was rugby tackled by an officer.

In the melee, the guard had left the prison truck's engine running and three of the group sped away - smashing through an iron gate which fell onto another of the inmates.

Police have now launched a manhunt for the three escaped prisoners - still wearing chains - who were due to stand trial for drugs and theft charges.

The one man seen running away was caught shortly after a shootout with cops. Five of the ten prisoners did not get involved.

Corrections Department Director General Naras Savestanan blasted the ''reckless'' prison warden for leaving the key in the ignition.

He said: ''The driver made a mistake which allowed three men to escape. He was careless. We are searching for the and expect to find them for prosecution. I will travel to the area to co-ordinate the search.''

Officers recovered the stolen prison van at 11am after it was dumped in an orchard some 20km away. The men they are looking for are Tharathip Permlarp, 26, Krisada Ketnui, 36, and Pichit Klinocha, 31.