The open-scabbard knives or short swords are the traditional
ban of the Lepcha people of Sikkim, but Lepchas are also in northern Bhutan and even eastern Nepal. "Drukpa" weapons in the north of Bhutan generally have a closed scabbard. (And in the south of Bhutan are many Nepalis who carry kukris.)
The knife in question is more decorated, but its hilt resembles this seemingly Tibetan knife on the Therion Arms site:
http://therionarms.com/antiques/com072.html