They will be taken to a nearby helipad with a police motorcycle escort before being flown to the provincial capital of Chiang Rai for treatment in a hospital there.
The boys were taken to the hospital, Chiang Rai province acting Gov. Narongsak Osatanakorn, who is heading the operation, said in a Sunday night news conference. A defence ministry official earlier told AFP six boys had "come out".
Earlier, 13 foreign divers and four Navy Seals guided the boys - with an adult in front and behind each child - through the narrow and submerged passageways.
The official heading the operation to rescue 12 boys and their soccer coach from a cave in northern Thailand says the operation is going "better than expected".
"Today is a D-Day for our operation", Narongsak said.
Osotthanakorn told reporters there would be a meeting Sunday evening to plan next steps, and that authorities want to ensure conditions are stable before beginning the next phase of the rescue.
The boys, aged between 11 and 16, went missing with their 25-year-old coach after soccer practice on June 23, setting out on an adventure to explore the cave complex near the border with Myanmar and celebrate a boy's birthday. The boys are between 11 and 16 years old.
Rescuers hope to extract the remaining eight over the next two days, although there are concerns that further monsoon rainfall will hamper efforts.More news: England clinch first World Cup shootout win in intimidating sea of yellow
But the governor supervising the mission said earlier that mild weather and falling water levels over the last few days had created optimal conditions for an underwater evacuation that won't last if it rains again.
"We need to refill", Narongsak said.
Authorities in northern Chiang Rai province began the unsafe mission to bring out the 12 boys and their soccer coach earlier on Sunday.
The boys and the coach will dive out of the cave one at a time, each accompanied by a member of a team of worldwide and Thai divers, officials said.
On Friday, Thai officials said the boys were working to build up their strength, but were not yet ready to navigate their way through small underwater passages - which can reportedly take an experienced diver around five hours.
Families of the children have been waiting anxiously for news following authorities' decision to initiate the rescue attempt at 10 a.m. local time Sunday, as storm clouds threatened to dump more water on the flooded caverns, undoing efforts to drain them. We will have to do the next mission as successfully as the one we did today.
Elon Musk has also dispatched engineers from Tesla, Space X, and the Boring Company. But they remain "at war with water and time" as torrential monsoon downpours deluged the Tham Luang cave, in the hilly jungle of northern Thailand, and threatened to flood it even further.
The mission reportedly paused due to depleted oxygen levels in the cave. It was not immediately known if a USA diver was among them. With love." "Don't be anxious, I miss everyone.