Then another four of the youngsters were successfully brought out of the cave, with the first rescue carried out shortly before 5pm local time, a few hours after the mission entered its second day.
Thai doctors have said they did not know what type of unusual illnesses the boys may have picked up in the cave. "We were extremely fortunate that the outcome was the way it was".
"This has been the largest, most complex cave rescue in history".
He said the boys, ranging in age from 11 to 16, were "incredibly resilient".
He said: 'The important thing is... personal space.
A clip released by Thailand's Incident Command Press Centre on Wednesday shows the boys in a Chiang Rai city hospital ward, wearing green surgical masks and tucked under white blankets, as they recover from their 18-day ordeal in a waterlogged cave.
Getting them out - which involved teaching boys as young as 11 who were not strong swimmers to dive through narrow, submerged passages - proved a monumental challenge.
Chaiwetch Thanapaisal is director of Chiang Rai Prachanukroh Hospital.
One member of the final group of four boys and the coach who arrived at the hospital Tuesday evening had a slight lung infection, Thongchai said. Three boys from the last group saved have ear infections.
Rescuers Begin 'Challenging' Final Push To Free Last Five From Thai Cave
The rescuers have been learning from experience and were two hours faster in bringing the second batch of survivors out on Monday. CNN was told the boys were exploring the caves on June 23 with their coach when they were trapped inside by heavy seasonal rains.
First pictures have emerged of the schoolboys recovering in hospital after being rescued from a cave in Thailand on Tuesday.
"As you can imagine from what's been in the media all week it is not a holiday that Harry has been on", Pearce said.
The boys and their coach went missing after football practice on June 23, setting out on an adventure to explore the cave complex near the border with Myanmar and celebrate a boy's birthday.
But the initial euphoria at finding them dissipated as authorities struggled to devise a safe plan to get them out, with the shelf more than four kilometres (2.5 miles) deep inside the cave and the labyrinth of tunnels leading to them filled with water.
The final four boys and their 25-year-old coach were evacuated from the cave by a team of Thai Navy SEALs and worldwide cave diving experts with just a few hours to spare before pumps holding the floodwaters failed.
The rescue efforts cost the life of one rescue worker - a former Thai Navy Seal ran out of air inside the cave system.
After seeing the news of the trapped 12 "Wild Boars" football players and their coach on TV, they collected donations from fellow villagers for their flight before departing for Chiang Rai and the cave. He said, "The situation went beyond just being a rescue mission and became a symbol of unity among man". "Everyone worked together without discrimination of race or religion as the ultimate goal was to save the youth football team".
Rescue mission chief Narongsak Osottanakorn said: 'We don't see the children as at fault or as heroes.