A further four boys and their coach, Ekaphol Chantawong, remain trapped amid a race against time and rising water levels.
A Thai army commander said the operation went “smoothly” but warned the next phase “will depend on all conditions”, with rain forecast for the coming week.
Those rescued so far are said to be in good health.
The latest group, assisted all the way by expert divers, made their way through a labyrinthine flooded cave complex.
They were carried out on stretchers, still wearing their full-face diving oxygen masks, and cared for at a nearby field hospital.
The boys were then airlifted to Chiangrai Prachanukroh Hospital, where the four young players rescued on Sunday are recovering.
The health of the five people still trapped is “still good” according to officials who have not confirmed identities to parents.
Amid fears of infection, parents have been told there will be “no hugging or kissing” until health checks are completed.
After a examination by a doctor, the weakest of the boys were evacuated first.
The boys, many of whom cannot swim, are effectively being pulled through tunnels by expert divers.
The 12 youth team players and their 25-year-old coach went missing on June 23 after becoming trapped by rising floodwater in Tham Luang Nang Non cave in northern Chiang Rai region.
The Thai navy SEAL unit that has been overseeing the rescue confirmed that the total number of boys brought out was now eight.
Some of the parents said they had not been told who had been rescued and that they were not allowed to visit the hospital.
The rescued boys have not been identified “out of respect” for the families whose sons were still trapped.
Medical teams previously said concerns included hypothermia and an airborne lung infection known as cave disease, which is caused by bat and bird droppings.
Thirteen foreign and five Thai divers make up the main team guiding the boys to safety through narrow, submerged passageways that claimed the life of a former Thai navy diver on Friday.
The cave complex is off-limits during the rainy season, which usually runs from May to October, when downpours can quickly flood it.
Relatives said the boys had had set out to explore the cave for a picnic to celebrate a birthday.
A sudden downpour caused the water inside to rise, leaving them trapped.
Gianni Infantino, president of football’s governing body Fifa, has invited the boys to the World Cup final in Moscow on Sunday.
Meanwhile, medical experts warned that some of the boys may never be able to swim, be in the dark again or in rooms with closed doors.
Dr Jennifer Wild, a consultant clinical psychologist, said that such everyday happenings may bring back traumatic memories.
She said the boys need to view the ordeal as an “unusual adventure”, rather than an event that nearly killed them.