Weakest extracted from the cave first

An Australian doctor convinced Thai officials to change their rescue plans and first get some of the weakest boys out of the cave where they were trapped, it can be revealed.

Cave diver and anaesthetist Dr Richard Harris, from Adelaide, dived with the rescue team on Sunday afternoon to check on the 12 boys and their coach.

The initial strategy was to extract the strongest boys first because they would have more chance of making it to safety while the others could stay back and build up strength.

But that was revised after Dr Harris' health assessment found some of the weaker boys may not survive if they were left behind, according to Thai media.

Children pray for the Thai schoolboys at a school in Ahmedabad, India. Photo: Reuters

Four of the 12 trapped boys were brought to safety on Sunday evening. Operations to bring out the other eight and their coach started yesterday afternoon as divers placed fresh oxygen tanks along the exit route.

Dr Harris, who was requested by British divers leading the operation, is working alongside the Thai Navy and 18 other Australians in the rescue efforts.

The 53-year-old has 30 years of diving experience and has worked on retrieving bodies from caves.

He famously found the body of stunt diver Agnes Milowka who ran out of air in the Tank Cave near Tantanoola in the south east of South Australia in 2011, The Advertiser reported.