There has been no contact with the boys, aged 11 to 16, and their coach since they went into the cave last weekend and were hemmed in by heavy rains that blocked the entrance.
Those downpours have continued all week, hampering the enormous rescue efforts to find the youngsters and their 25-year-old coach.
Medical teams staged drills on Saturday to prepare for their possible rescue as worries loomed over how the boys might be pulled out of the Tham Luang cave if and when they are found.
Ambulances and helicopters were on standby for the drills Saturday morning at the bustling rescue site in northern Chiang Rai province.
"It's to set up a system to practice what to do until we can get them to hospital," Chiang Rai governor Narongsak Osottanakorn said late Friday.
As the search for the boys hit its seventh day, attentions turned to their chances of survival inside a cave with little or no food and light.
The boys likely have access to fresh water -- either dripping in though rocks or rushing in through the entrance -- but experts warned that runoff water from nearby farms could carry dangerous chemicals or bacteria.
"If they drink the water in the caves and it makes them sick it could hasten the problem that they're in, but if they don't drink it then they're also in trouble," Anmar Mirza, coordinator of the US National Cave Rescue Commission, told AFP.