The footage, released by Thai officials Wednesday, shows eight of the boys sitting up in their hospital beds, clad in hospital gowns and face masks.
The "Wild Boars" football team got stuck inside the cave on June 23 after flooding caused by heavy monsoon rains blocked the entrance.
"To not receive food, we can still survive for many months but what's necessary is water, which the cave has, and around this time there's a lot in the cave, and they chose clean water to drink", he said.
They will remain in hospital in the nearby city of Chiang Rai for a week, followed by a week's recuperation at home.
Seeing his son through the glass, he only wanted to hug him, he added.
Pure Flix Entertainment, an Arizona-based Christian film studio, said it's seeking the movie rights to the harrowing mission to rescue the soccer team and their 25-year-old coach from the flooded cave.
Another new video clip to emerge on Wednesday came from the Thai Navy SEAL team which led the rescue effort, showing them pulling at least one of the boys through the cave on a stretcher, heavily sedated.
Among them were the last three Thai Navy Seals and Australian doctor Richard Harris, who had spent much of the past week keeping vigil with the trapped boys, the Guardian said.
"Some of them were asleep, some of them were wiggling their fingers".
One of the British divers said: "I was told the boys were given a dose of ketamine [a horse tranquilliser often used as a recreational drug] to keep them calm". Highlighting the dangers, a former Thai navy SEAL volunteering to work on the rescue died Friday while replenishing oxygen canisters placed along the escape route. That won't happen or we'll give them hell.
The group became trapped in rising floodwaters and were found nine days later emaciated and disheveled on a muddy ledge, with water lapping ominously below.
"It was mostly a matter of clambering through mud, which was very tough", Ben Reymenants said.
Ivanhoe Pictures president John Penotti on Wednesday issued a statement saying that Thailand's Navy and government had selected the company for the film adaptation of the almost three-week ordeal.
USA media quoted the company as saying the film would be directed by Jon M Chu.
"We did something nobody thought possible", the acting governor of Chiang Rai province, Narongsak Osatanakorn, said once the 18-day ordeal was over.
UK football team Manchester United invited the team as well as their rescuers to the Old Trafford stadium next season.
They are malnourished and weak, and doctors are anxious that they could be susceptible to germs spread by family members or other visitors, Dr. W. Ian Lipkin, a Columbia University infectious diseases expert, says. "I'm happy that the boys are out too", said Khamluh Guntawong, the grandfather of team coach Ekkapol Chantawong.