An Australian SAS veteran says Canberra is failing to back veterans struggling with post-traumatic stress disorder as suicide rates climb.

An Australian veteran cycling from Hanoi to Sydney to raise funds for veterans suffering from post-traumatic stress disorder (PTSD) says Canberra is failing returnees struggling with the disease.

Laurie "Truck" Sams, 67, from Queensland and a Special Air Service (SAS) veteran from the Vietnam War, has struggled with PTSD at huge personal cost after serving in Vietnam's Phuoc Tuy province in 1970.

"I'm not satisfied until there is 100 per cent (effort) looking after the vets. They are just not being looked after," Sams said.

"There are many young veterans slipping through the net - committing suicide," he said.

"They are young veterans that have come back from Afghanistan," Sams told AAP.

Queensland-based charity, Walking Wounded, reports that since 1999 49 soldiers have been killed while on active duty but it has seen 239 veterans commit suicide.

"There's got to be something set in place to look after these veterans as soon as they come back," Sams told AAP during a stopover in Thailand.

He says the present bureaucratic processes veterans face in clinically proving they suffer from PTSD is "demeaning".

For Sams his suffering from PTSD led to family breakdown.

"It took 20 years for the effect - hard effects. It cost me my family. I was crawling the hallways at night and thinking that was normal - but it wasn't - in my sleep," he said.

As a young boy Sams saw his father - a veteran of the Second World War in the Pacific - suffer from PTSD.

"He was a very bitter man against the Japanese. And he sat in a room at night time in the dark and drank a lot of alcohol until he was really drunk."

In 2001 Sams was awarded Australia's Star of Courage for saving his tandem parachute student in a parachute accident in 1995. That accident cost him the lower part of a leg and he now wears a prosthetic.

But being an amputee has failed to hold him back. In 2002 and 2005 Sams and other veterans walked the Thai Burma "Death" Railway.

His latest adventure is cycling 10,000 kilometres from Hanoi to Sydney to support those veterans suffering from PTSD and other injuries.

"I wanted to cover all of Vietnam to Australia which was 10,000km because it was a 10,000 day war," he said.

In Vietnam Sams met with Vietnamese veterans - his "former enemy" - in a dialogue of five hours that marked a "very big healing process".

Sams says his campaign will continue for better treatment for veterans suffering PTSD when he returns to Australia, including hopes of a meeting with Prime Minister Malcolm Turnbull.

"The younger veterans, they've got their finger on the pulse with (the issue). I'm sure we'd be able to have some dialogue, [even] with the prime minister himself," he said.

Sams has been joined by other ex-SAS veterans, Troy Lockyer, 43, and Giles Beresford-Peirse, 47, to ride to Southern Thailand's Surat Thani.

From there another SAS vet Matt Brown, 50, will join Sams for the 1220km leg to Singapore before flying to Perth to tackle the Nullarbor to the Australian east coast, with a goal of arriving in Sydney on November 20.