It seems you have a Taotie depicted on the upper part of the scabbard.
https://fr.wikipedia.org/wiki/Taotie
The guard seems an unusual feature for Bhutanese weapons
I would rather say a vintage or touristic knife.
For the origine .... Difficult to say. You pointed out some nepali features. Taotie are depicted in Nepal, Tibet and China. Coral and turquoise mostly used in Tibet/Nepal.
We can probably narrow to Nepal/Tibet