"May God bless you!"
Volunteers at the Tham Luang cave were shaken by the diver's death.
Saman set out on the challenging mission at 8:37pm local time on Thursday, successfully reaching the cave with the cargo.
Passakorn Boonyaluck said Saman Gunan had volunteered to help with the rescue.
"We lost one man, but we still have faith to carry out our work".
Ivan Karadzic on Friday at the rescue site in Chiang Rai. "On the way back from setting up oxygen bottles, Petty Officer First Class Gunan passed out".
"The operations are still going on", and the effort to rescue the children as soon as possible would continue.
Authorities now say there are concerns about falling oxygen levels in the chamber where the boys and their coach are trapped.
Thai officials have stated that today's death will not slow down rescue efforts, as additional divers work to install extra oxygen tanks along the cave's tight and hard flooded passageways.
Two weeks back a young football team along with their coach got stuck inside a cave in Thailand.
Chiang Rai Governor Narongsak Osotthanakorn said they were "racing against water".
The trapped team has been receiving basic training in breathing through diving equipment in case the order to evacuate is given.
Les images de l'évasion de Redoine Faïd - LINFO.re - France, Faits divers
L'hélicoptère qui a permis au braqueur de s'évader a été retrouvé quant à lui dans le nord de la région parisienne. Ils avaient tiré notamment sur une voiture de police municipale, tuant Aurélie Fouquet et blessant son coéquipier.
About 120 million liters of water had been pumped out by late on Tuesday, or about 1.6 million every hour.
But heavy monsoon rains are forecast for Sunday.
"Our biggest concern is the weather".
The conditions of the boys and their coach will affect how and when they are extracted, Osatanakorn noted, saying they may not all be taken out at the same time.
Few of the boys are able to swim, and none of them have any diving experience.
The Thai navy is teaching the boys the basics of diving, with a view to guiding them out through flood waters.
Even rescuers, all highly trained professionals, are taking six hours just to get to where the boys are located, said online reports.
"We thought that we might have the expertise to help since we have climbed to collect bird's nests for generations".
Other options are also being explored, including scouring the mountainside for other ways into the cave.
"We are draining as much as we can", said Khao Khieupakdi, a Bangkok disaster prevention official.
"Although water levels have dropped, the diving conditions remain hard and any attempt to dive the boys and their coach out will not be taken lightly because there are significant technical challenges and risks to consider", the British Cave Rescue Council said.
The group was discovered on July 2 after 10 days totally cut off from the outside world.
But that option is a last resort and may have to be taken off the table if flooding worsens.
A video released by the SEALS showed two rescuers seated on an elevated part of the cave beside boys wrapped in emergency foil blankets who appeared to be in good spirits, occasionally laughing. But you run the risk of causing another collapse.