"Extracting the children takes a lot of people", the deputy prime minister told reporters.
On the rescue plan, Gen Prayut said there are two methods in which the trapped group can come out.
The world watches with bated breath while the boys - who have been stranded for nearly two weeks now - are reportedly being trained in how to breathe with scuba equipment as they prepare for a possible attempt at leaving the cave this morning.
Seven of the navy team, including a doctor and nurse, spent Tuesday night in the dark with the boys and their coach, who have been trapped inside the cave since June 23.
The footage, published on the Thai Navy SEAL Facebook page, runs by 11 of the 13 members of the team, each makes a traditional Thai greeting gesture to the camera before introducing themselves by nickname and saying "I'm in good health".
The boys were being given rudimentary diving lessons Wednesday, even though none of them knows how to swim. The group were found on Monday after nine days stranded underground by rising waters.
Video released early on Tuesday by the Thai navy showed the boys in their football uniforms sitting on a dry area inside the Tham Luang Nang Non cave above the water as a spotlight from a rescuer illuminated their faces.
Pictures also showed a navy Seal treating minor cuts on the feet and legs of the boys.
Telephone lines are being reeled into the cave so as to help the boys talk to their relatives, Mr Narongsak said.
Kian Kamluang, whose 16-year-old son Pornchai is inside, said she had thought it was a 50 per cent chance that her son would be found.
Another is to let the boys dive, which is not easy as the passageways are twisting, he said, adding the group would be taken out one by one while their readiness must also be assessed.
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Rescue crews have also been staging rehearsals for how they would remove the boys by ambulance from the scene after they emerge.
He returned Wednesday to offer prayers for their safe rescue, and as measure of the respect in which he was held, was allowed access to the cave, which is generally off-limits to outsiders.
He said the team is now recuperating.
In a press conference Wednesday morning, Chiang Rai governor Narongsak Osottanakorn said it would be "difficult" to bring them out Wednesday.
He said it was unknown if an evacuation involving diving could be attempted.
"We have the luxury of time", Courtley said, noting that the group is now in a "stable and non-life threatening" situation in the cave. If the condition is right and if that person is ready 100 percent, he can come out. He said authorities will evaluate their readiness each day and if there is any risk will not proceed.
"I hate to say this, but some of these kids are going to die in an effort to try and bring them out using dive equipment", he added.
The newspaper reports it has been told that fast-water currents inside the cave have eased to a standstill and with monsoonal rains expected to resume by Friday, conditions for the rescue are as good as they are likely to get. This could take anywhere from days to weeks to even months as the rainy season typically lasts through October.
"We are talking kilometers of transport under the water with zero visibility", said Claus Rasmusen, a certified cave diving instructor based in Thailand who has been helping Thai SEAL team with logistics.
"Instructions were given by the King that everyone [rescuers] must bring out the children as quickly as possible", Gen Prawit said.
"Nobody will teach anyone a full cave course, but trying to get them comfortable with masks, with the breathing, (is) completely different", he said.