Maintaining air supplies inside the cave has become the "top priority" as rescuers face the prospect of the boys remaining underground throughout the monsoon season, which ends in October.
Twelve boys and their coach, who had been missing since last month, were found by a pair of British cave divers late Monday.
He added: "They can not decide how many of them will be able to come out for the first operation".
"There are probably many complexities that are hard to appreciate without being there in person", he added. That's the name of the young boys' team.
On Thursday their parents sent letters in for the boys to read - but the governor said he was not sure if these had reached them yet. Heavy rains are forecast for this Sunday, and the boys are now being trained in the use of scuba diving gear while the Thai Navy Seals prepare the 5km-long route for their anticipated evacuation.
According to Maj. Gen. Chalongchai Chaiyakam, the 13 "will continuously come out in approximately 2-4 days, which all may change depending on weather and water conditions".
Putin and Trump may meet without aides in Helsinki
However, he took issue with President Trump's statement that he planned to discuss Crimea with President Putin there. Trump is slated to meet Putin in Helsinki on July 16.
The rescue operation has proven challenging to date as swimming to safety could take about five hours and would require navigating through tight and dark passageways.
It is unclear at this point if Thai officials will accept Musk's offer for help. "They are now at the field hospital near the cave", Tossathep Boonthong, chief of the health department in Chiang Rai in northern Thailand, told Reuters.
The coach, who has faced criticism for taking the boys out in the cave, also wrote an apology note addressed to his players' parents.
"Now and in the next three or four days, the conditions are ideal in terms of the water, the weather and the boys' health", he told reporters this afternoon. Moreover, the design is robust, so any bumps or collisions along the dark narrow water-filled passages will not jeopardize the integrity of the sub. It would still be a harrowing and claustrophobic experience, but-if everything works as Musk describes-it could be much less risky than conventional scuba diving, where a panicking teenager could lead to the death of the teen himself as well as his professional scuba guides.
Rescuers took advantage of a break in the rain to launch the mission much earlier than originally expected. Crews located the boys about two kilometres from the cave's entrance following nine days of searching.
Dozens of divers have arrived at the cave on Sunday morning.