Rescue officials were hopeful that the final four boys and their coach would be rescued Tuesday.
Divers are on their way in the third rescue journey deep into a flooded cave with a mission to complete the job and save everyone inside.
Musk says he hopes the device could help in the rescue of the remaining people.
He said they got an earlier start than on the previous two rescue days, Sunday and Monday, and felt confident in the experience gained.
Officials were not immediately available to comment on who had been brought out, and it was not clear what condition they were in.
He said the next operation will be conducted on Tuesday.
The 12 boys, part of a football team, and their coach were stranded in Tham Luang cave in northern Thailand on June 23.
The 8 boys who have already been taken from the cave by diver are thought to be largely healthy after their ordeal, despite having been trapped inside the cave with little food or water for more than two weeks.
The next rescue operation is planned for Tuesday at 10am BST (4pm Thai local time), but Mr Osatanakorn said he can not promise the remaining five would be rescued by the end of the day.
Depicting boys stuck inside the cave, the message on the sculpture read, "We pray for the safe rescue of the Thai boys".
"The boys are still requesting the Thai basil fried rice, but they're not allowed to eat it yet", they said.
Experts warned that drinking contaminated water or otherwise being exposed to bird or bat droppings in the cave could lead to unsafe infections.
"The kids are footballers so they have high immune systems", Mr Jedsada said. They successfully extracted the second group of four a full two hours faster than the first, officials said.
"Today (Tuesday) we hope to be faster", Narongsak added, of the complex and risky operation that involves diving through narrow, flooded chambers.
Some of the divers, whose job was to place oxygen tanks along the treacherous underwater route, said visibility was near zero and the path was extremely risky. "Everyone is in high spirits and is happy to get out".
The cave complex is regularly flooded during the monsoon season which lasts until September or October.
The rescue operation continued today and saw four more boys freed.
In the past two days, eight boys were rescued and are now in a hospital isolation ward while they are tested for any possible infections.
Elon Musk really wants the world to know he's at the cave rescue operation site in Thailand, and he's there to help. "Mini-sub is ready if needed".
The youngest member of the Wild Boar team in the cave is just 11 years old.