He was taken by helicopter and then ambulance to the hospital in Chiang Rai were the first four boys, who were rescued on Sunday, are now being held in quarantine as they undergo tests. But officials waited several hours before confirming their rescue.
Nargonsak said this phase may take longer than the previous two rescue missions.
The eight boys who've been rescued so far have all swum out of the cave, each escorted by two expert divers.
At least nine ambulances have been waiting at the site after the leader of the rescue operation said Tuesday's aim was to bring out all five as well as a medic and three Thai Navy SEALS, who have been with the trapped boys.
Rescue crews ready themselves to go back into the cave.
Today's mission is expected to take "equal to or better than yesterday if we don't have any abnormal factors", Chiang Rai governor Narongsak Osottanakorn said.
The perilous rescues have involved two divers accompanying each of the boys, all of whom have been learning to dive only since July 2, when searchers found them.
Rescue teams have already extracted eight Thai boys from the cave, and all are recovering from their ordeal in hospital and said to be in good health.
He said two of them possibly have a lung infection but all eight are generally "healthy and smiling". All are now recovering in hospital. Relatives were able to see them through a glass partition, Narongsak said.
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One of the concerns, health authorities could be holding is the risk of "cave disease" - histoplasmosis - which can be contracted by breathing in bat or bird droppings.
A tenth boy has emerged from deep within a cave complex in northern Thailand, the second to be rescued on the third day of a huge worldwide operation to save the boys and their coach.
"I want to take my friends to lunch and we will play football together", he told Reuters.
The four were the first of the 13 Mu Pa team members who were evacuated from the cave since they became trapped on June 23.
This brings the total number of boys rescued from the Tham Luang cave complex up to 11.
The painstaking rescue has required breaks to allow the group of 18 elite divers to rest and replenish the cave with oxygen for the remaining soccer team members, ABC News reports.
The ups and downs of the rescue bid have entranced Thailand and also fixated a global audience, drawing comments of support from celebrities as varied as US President Donald Trump, football star Lionel Messi and tech guru Elon Musk.
Musk tweeted Tuesday morning he'd "Just returned from Cave 3, ' referring to the rescuers" command center inside the sprawling cave.
The billionaire Tesla chief has visited the Tham Luang cave to drop off a miniature submarine he hoped might help with the ongoing rescue operation of the Wild Boar soccer team. "Leaving here in case it may be useful in the future".