They tried to install the cable on Tuesday but the equipment was damaged by water.
Once the cable is installed, people will be able to make phone calls to the cave, communication technician Phoowanart Keawdum told the AP.
The Thai Navy SEALs posted a video of the team, dated on Tuesday, in which the boys and coach said they were fine and greeted people outside the cave.
The boys, who are aged between 11 and 16, and their 25-year-old coach are being given swimming and diving lessons as part of plans to extract them from the cave. If water levels fell and the current weakened, they would be able to get out sooner.
A team of divers, medics, counselors and Navy SEALs have been staying with the team in the cave since they were found on Monday after a nine-day search.
The Tham Luang cave system in Chiang Rai province, northern Thailand, is made up of a series of dark, narrow bends. The cave is also currently partially flooded due to the sudden influx of rain.
The cave was most likely dry when the soccer team entered on June 23, but rushing waters later clogged the way back with mud and debris, rendering many of the exit routes difficult to pass through and with zero visibility.
Water levels in the cave are expected to rise as the summer goes on, as Thailand’s rainy season usually lasts from May until October.
As of late Tuesday, about 120 million liters of water have been pumped out of the cave.
The map below shows a overview of the Tham Luang cave network: