Why So Difficult to Find Rai Khulung

Why so difficult indeed..?

Maybe you don't have the credibility you need to get someone who speaks the language to answer your request?
After all, you are from Canada, living in Vietnam (by your profile), and asking for someone who would speak a totally unrelated language. While at the same time you are asking in a different post for someone speaking Chinese and Cambodian, two other unrelated languages...
Explaining 'why' you would need all this could help improve your credibility and might get you a more helpful response?

Then, 33,000 people on 28,000,000 inhabitants is only 0.12% of the people in Nepal speaking this language. This forum has only a couple of thousands visitors and just a handful of active posters. My guess is that 0.12% of them is not one full person yet, and you have just not been lucky enough to get in contact with someone speaking your requested language yet. Your first post has only been read by 104 people up to this moment...