One of the divers who played a critical role in the rescue of the 12 Thai soccer boys and their coach believes the kids would not have made it out had they not been drugged.

Retired Perth vet Craig Challen and Adelaide anaesthetist Richard "Harry" Harris have recounted details of the rescue mission that gripped the world, supported by divers from Thailand, the UK and Europe.

Speaking on their return to Australia and still in disbelief over the miracle result, Challen said the boys were medicated to the extent "they didn't know what was going on".

"They had drugs," he told the Sunday Telegraph.

"We could not have panicking kids in there, they would have killed themselves and possibly killed the rescuer as well."

A British driver involved in the rescue initially said the boys were given ketamine but Thai Prime Minister Prayuth Chan-O-Cha clarified that it was an anti-anxiety medication, and that they were still conscious.

"Who would chloroform them? If they're chloroformed, how could they come out? It's called anxiolytic, something to make them not excited, not stressed," he said at a press conference in Bangkok.

But a British diver said: "I was told the boys were given a dose of ketamine", referring to the horse tranquilliser often used as a recreational drug.

An American diver involved in the rescue that the "kids were proper knocked out".

Spanish diver Fernando Raigal told the Daily Mail: "The boys were sedated — they were unconscious".

Harris has also shared an emotional account of how their Thai cave rescue mission became a reality.

Sitting at the back of an RAAF C17 aircraft with Australian authorities, Dr Harris wrote of his musings with Challen, his right-hand man in the risky operation.

"I feel like it is the first opportunity to really stop and reflect on the extraordinary events of the past 8 days since Craig and I were deployed as a small AUSMAT team to the rescue in Chiang Rai in Northern Thailand," Dr Harris wrote.

Local and British divers who Dr Harris described as "the awesome foursome" had already laid terrific groundwork to ensure the success of the gruelling mission, he stated.

"They had already been doing the most extraordinary dives through the cave and laying the very robust rope which made all subsequent dives to the soccer team not only possible, but safe," he wrote.

"The efforts and skill of these guys in blazing this trail cannot be underestimated.

"The 4 Brits then did further supply dives to the soccer players, the coach and the four Thai Navy Seals which allowed them to prepare and sustain themselves for the rescue ultimately."

Dr Harris praised Thailand's efforts during the rescue mission, and the huge assistance provided by the international community.

"(They provided) everything from catering, communications, media and of course the huge teams of workers filling the cave with tonnes and tonnes of equipment to try and lower the water and sustain the diving operations," he wrote on Facebook.

"I have never seen anything like it with man battling to control the natural forces of the monsoon waters."

He said the Facebook post was a way of thanking all the people involved.

"I wanted to write this to try and give credit to all the people who were in some way involved. Craig and I have had a spotlight on our efforts and we want to make everyone realise that while we might have become the face of this rescue for some reason, everyone should know that the role we played was no more or less important than all the many hundreds (perhaps thousands) of people I have mentioned," Dr Harris wrote.

Dr Harris and Challen touched down with 20 Australians involved in the dangerous rescue.

With them were six Australian Federal Police cave divers, one Defence diver and a support crew member who was described as integral to the rescue operation.

The Australian Defence Force flew the entire crew home on RAAF jet which left Thailand on Friday.

Their return came as parents of the 12 boys, all members of the Wild Boars soccer team, made it clear they had no blame for the boys' junior coach, Ekkapon "Ake" Chantawongse.

The boys are understood to have entered the cave as a part of a team ritual, where younger boys would carve their names on to the wall.