Volunteer diver Saman Gunan lost his life on 6 July while installing oxygen tanks in the flooded cave complex.
He has since been hailed as a hero around the world.
The boys and their 25-year-old coach were told of his sacrifice only on Saturday, when doctors decided they were strong enough to process the news.
"All cried and expressed their condolences by writing messages on a drawing of Lieutenant Commander Saman and observed one minute of silence for him," said Jedsada Chokdamrongsuk, permanent secretary at the health ministry.
