The health of the four boys and their football coach is said to be good as they ready to be guided through the narrow flooded passages of the complex.
Eight boys have been brought out of the caves over the past two days.
The operation inside the Tham Luang caves has attracted global attention.
The group became trapped on 23 June after heavy rains caused flooding. They were found last week by divers.
How are the rescued boys?
The eight boys have not been seen in public, but have been pronounced to be in reasonable health.
