This is one of the more legendary places to stay in Northern Thailand (and was probably the first guesthouse in Mae Hong Son Province). It's run by John Spies, an expert on the area, with rooms and bungalows ranging from basic options with shared bathrooms to still rustic but comfortable ones with more space. All perch on a hillside overlooking Nam Lang.
Choose from caving and kayaking trips (the latter is possible from approximately February to May), guided or unguided hikes (good maps are available) or just hang out in the beautiful communal area. The traditional Shan herbal sauna is an experience, and the custom ovens bake bread and other treats. Tham Lot is a short walk away.