A tunnel cave connecting a sink in the downstream end of valley in pinnacle karst to a resurgence at the rim of (the locally) shallow limestone outcrop below Matrongkol. An inspiring entrance (15m wide, 3.5m high) leads to a boulder collapse obstructed by driftwood but a squeeze to the top of a 2m climb down gains a dirty, shallow pool from where a north-south running passage (on average 7 m wide, 2.5 m high) continues below a daylight window (15m above) to enter a Y-junction. Here North South passage turns to the right, continuing all the way (185m, inclined by-7º) to the resurgence as a North-North East-South-South West passage. Some 50m from the Y-junction, the main drag splits into two parallel 20m-passages (the right/north-western one requires swimming but the left is dry). They unite at a cross-rift chamber, split again, and re-unite once more to continue from then onward as a level passage to a daylight-lit collapse area at the rim of the limestone outcrop.