Local man Ho Khanh discovered Son Doong in 1990 while searching Phong Nha-Ke Bang National Park for food and timber to earn a modest income. During his search he stumbled across an opening in a limestone cliff, noticed clouds billowing out from the entrance and heard the sounds of a river raging from somewhere inside. He returned home and forgot about the cave.

Ho Khanh met Howard and Deb Limbert of the British Cave Research Association (BRCA), who were conducting exploratory caving expeditions in the area. After hearing his stories, they urged Ho Khanh to rediscover the cave, which he eventually did in 2008, after several attempts. In 2009, he led Howard, Deb and a team of other caving professionals to the opening. After the first survey in 2009, the team were able to conclude that the cave had the largest cross-section of any cave anywhere on the planet.

The cave was named “Son Doong” and Ho Khanh is still an integral part of every Son Doong Expedition