Tales told by Norman Olsen to support his claim for post-traumatic stress disorder included casting himself in a role befitting kung-fu action hero Bruce Lee, taking on a gang of 12 Vietnamese thugs in a Hong Kong bar brawl in the early 1970s.

The Administrative Appeals Tribunal was told how the digger single-handedly battled the gang who were armed with spiked batons and acted like "crazed lunatics ... screaming and yelling" and left just two of the men standing before he escaped.

Other yarns spun by Mr Olsen to the tribunal featured hand-to-hand combat against a Vietnamese guerrilla he found hiding behind a rock, and enduring anti-aircraft fire while flying over the battlefields. They were also taken with a grain of salt by the AAT.

The disability pensioner applied to the military repatriation commission for a boost to his pension, arguing the dramatic events of 1969 to 1971 left him with post-traumatic stress disorder and when he was knocked back, he appealed the decision to the AAT.

But tribunal member Marella Denovan has rejected Mr Olsen's claim, finding that he tended to tell rambling tales, painting himself in a heroic role at the centre of the action.

A medical witness told the tribunal that Mr Olsen's claims of being terrified in Vietnam were not consistent with his bragging about punching and assaulting people.

Mr Olsen's case was not helped when his advocate invoked the displeasure of the tribunal by trying to coach witnesses during breaks in the hearing in October, to get them to back-up the veteran's versions of events.

Investigators working for the Department of Veterans' Affairs debunked the Queenslander's key stories of the events that left him suffering from PTSD.

His tales of witnessing the accidental death of a comrade on his first day in Vietnam, of coming under fire and then bashing an insurgent with his rifle were not credible, the tribunal found.

Mr Olsen's claims of single-handedly fighting a dozen armed Vietnamese toughs, knocking several of them out, in bar in Hong Kong in 1971 stretched the patience of the tribunal too far.

"The account Mr Olsen gave conjured up images of a scene out of a Jackie Chan or Bruce Lee movie, Mr Olsen playing the role of the super hero," Dr Denovan found.

"It is totally incredulous."

Mr Olsen had previously convinced psychiatrists that he suffered from PTSD but the tribunal found these diagnoses were based on tales of events that had not happened.

Dr Denovan relied on the evidence of psychiatrist Dr Bradley Ng, who said it was more likely that the veteran, who has a history of drinking and brawling, was suffering from antisocial personality disorder, a condition that makes people more likely to deceive and distort.

"Dr Ng noted that for a man who claims to have been in fear in Vietnam, [Mr Olsen] talks quite boastfully about punching and assaulting people," Dr Denovan wrote in her judgement

"Dr Ng stated that unfortunately, people with antisocial personality disorder tend to deceive and distort accounts."

The tribunal accepted that Mr Olsen might have genuinely come to believe his account of events in his time in the army, but as an unreliable witness, his claim for a military disability pension had to be refused.

"I have concluded that Mr Olsen has a sincere belief that his psychiatric illness/s are due to his experiences in Vietnam, however he is an unreliable witness, and he was not exposed to the events the diagnosis of PTSD relies upon," Dr Denovan wrote.

"I therefore find that on balance, Mr Olsen suffers from generalised anxiety disorder, antisocial personality disorder, and alcohol misuse."