Bayin Nyi Cave is one of the limestone cave temples that make the countryside around Hpa-an so rewarding. The cave contains Buddhist shrines and images, while the surrounding karst landscape gives the approach much of its drama. Nearby hot springs add a practical reason to linger.
It is far enough from town that you should treat it as part of a cave-and-countryside loop rather than a quick urban sight. Go with a driver or on a bike route if conditions allow, carry water, and allow time for the slower rhythm of villages, fields, and limestone cliffs between stops.