I can highly recommend the Nar Phu Valley / Kang La Pass trek. It is located in a very remote part of the country close to the Tibetan border and only accessible by foot. It has lots of stunningly beautiful scenery to offer, you walk through majestic mountain ranges, high above deep river canyons (if you are afraid of heights it might bot be the right choice for you), see beautiful secluded monasteries and traditional stone house villages. My guide Rajan was really nice, helpful, and knowledgeable telling me a lot of interesting stories about the region and the people living there. He is very sensitive to the needs of people. You reside in very nice basic guesthouses, sitting around the fireplace for dinner with the most welcoming people. Even if you don‘t speak the same language you manage to connect on a very deep level. I have a lot of beautiful memories from this trip.