A former occupation of the trapped Thai soccer team's coach may be crucial in keeping the boys mentally healthy if authorities are forced to prolong their escape.

Rescuers are racing to pump water out of the flooded cave to safely remove the 12 boys and their coach, Ekapol Chanthawong, with minimum risk ahead of heavy rain forecast this weekend.

But as they approach more than 300 hours since being trapped, health professionals have warned of near fears for the boys' mental health.

It is hoped the 25-year-old coach will be able to use his experience as a Buddhist monk to help the boys as they face a potentially lengthy wait for freedom.

Chanthawong's aunt has revealed he spent 10 years as a saffron-robed monk, honing his skilling of meditation at a gilded temple in Thailand's mountainous north, where he still stays from time to time and meditates with monks each day.

"He could meditate up to an hour," said his aunt, Tham Chanthawong.

"It has definitely helped him and probably helps the boys to stay calm."

Medical experts say that although the boys are mostly physically healthy, after 10 days totally cut off form the outside world it is likely the ordeal will begin to take a mental toll.

"It's very likely that while the boys were in the cave but not yet discovered by rescuers that they experienced various degrees of anxiety, fear, confusion, vulnerability and dependency, and perhaps hopelessness," said Paul Auerbach, of the Department of Emergency Medicine at Stanford University's medical school.

Parts of the passage leading to a chamber where the team were discovered are still flooded all the way to the ceiling, making diving the only way out.

"What we worry most is the weather," Chiang Rai provincial Governor Narongsak Osatanakorn told reporters, adding heavy rain is predicted to start on Saturday.

"We can't risk having the flood back into the cave."

The governor said he's also spoken with Thai Navy SEALs about the whether they can take the risk of having the team, many of whom cannot swim, use masks and oxygen tanks to make their way through kilometres of muddy water.

Osatanakorn said he'd requested 13 sets of dive gear be prepared, just in case it's decided to bring the boys out before the water clears.

"This morning, I have asked for 13 sets of (diving) equipment to be prepared and checked the equipment lists and place them inside (the cave) in case we have to bring them out in this condition with less than 100 per cent readiness," Osatanakorn said.

The team of 12 boys aged 11 to 16 and their 25-year-old coach became trapped on June 23 when monsoonal rain blocked their exit while exploring the Tham Luang Nang Non cave system in the north of the province.

Earlier Osatanakorn said not all 13 would be extracted together, depending on their condition.

He said they have been practising wearing diving masks and breathing, but haven't attempted any actual dives as yet.

Officials have said they would prefer to bring the team out as soon as possible as heavy rain is expected to raise water levels inside the cave, making passage in some parts difficult if not impossible.

The Australian Defence Force confirmed it had sent two disaster recovery specialists to aid in the rescue, in addition to crews that were sent earlier as part of an international effort.

Australian Federal Police divers and other Australian support staff are assisting Thai Navy deliver food, water and first aid supplies to the group within the cave.

Fresh footage emerged yesterday of the smiling faces of the boys, clad in silver foil space blankets.

Seeing the boys has boosted the mood of their family members, and officials are working to install an internet cable to the cave so that parents can talk to their children.

Kian Kamluang, whose 16-year-old son, Pornchai, is in the cave, said she had thought there was a 50 percent chance that her son would be found.

"It's like he has been given a new life," she said, adding that she'll never let her son go into a cave or near water again.

Experienced divers are wary of taking out the boys through the dark and dangerous waters still in the cave, especially since they are untrained.

"We are talking kilometres of transport under the water with zero visibility," Claus Rasmusen, a certified cave diving instructor based in Thailand who has been helping Thai SEAL team with logistics, said.

"It's difficult."

The rescue mission has gripped the world's media and garnered support from the football world.

Austria and Leicester City star Christian Fuchs sent a video message of support yesterday.

"We have very strong ties with the country of Thailand, I'm closely following the rescue efforts to secure the lives of the 12 players and their coach," Fuchs said.

"I wish everybody all the best with their rescue efforts and I'm sure everything will be turning out well. Be strong."