Saman Kunont, 38, had been part of the team of Thai Navy Seals working to lay a 5km air pipeline from the cave entrance to the “Pattaya Beach” chamber, where a youth football team and their coach have been trapped for almost two weeks.

With so many rescuers working in the cave system, the oxygen content of the air is said to have dropped to as low as 15%, and such levels would make it difficult for the boys to survive in their chamber if rising monsoon floodwater should make an evacuation impossible.

Until a pipeline can be completed to pump in fresh air, O2 tanks are being delivered to the chamber to replenish exhausted supplies, as well as air tanks left along the exit route for use during a rescue.

Kunont and a buddy were reported to have set out from the rescue base at 8.30 local time on Thursday night (5 July) to deposit tanks along the exit route and had completed the task, but in the early hours of the following morning he became unconscious while still about 1.5km out, apparently in a dry section of the system.

His buddy tried to administer CPR, and when Kunont proved unresponsive he attempted to carry him back to the rescue base.

His death was reported as being caused by lack of oxygen, but it was unclear whether or not his breathing-gas supplies had run out.

A post mortem is being carried out, after which Kunont is set to receive a royal-sponsored funeral.

Much of the floodwater in the Thang Luam system has been pumped out, but with the threat of imminent rain the trapped boys are receiving basic scuba training in case an immediate evacuation becomes the only option.

Their weakened condition, inability to dive or in many cases even to swim, constrictions in the cave that would require removal of scuba equipment and strong currents, darkness and cold water are among the factors that make such an operation so hazardous.

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