Recently, I was wondering whether the plural of {Huch} is to be
treated as singular or plural.

Do we say {Huch law' wIghaj}, or {Huch law' DIghaj} ?

We have the Ca'NoN sentence:

{Quj wa'DIch monopoly Huch nav qa' tlhIngan QaS}
klingon forces replace original monopoly bills

Reading this at first, I thought that since the "klingon forces" is
plural, however we don't see a {lu-} on the {qa'}, then this means,
that the {Huch nav} is plural. But then I realized that perhaps only
the {nav} is the plural word of this noun-noun construction. So we
don't know (or at least *I* don't know) if the {Huch} here is to be
meant as singular of plural.

And, as americans say, I'm back to square one..

So, to return to the original question, does someone know if we say
{Huch law' wIghaj}, or {Huch law' DIghaj} ?

The Klingon Way has Huch nobHa'bogh verenganpu''e' yIvoqQo' Don't trust Ferengi who give back money. On the one hand, this has Huch nobHa'bogh verenganpu''e' instead of Huch lunobHa'bogh verenganpu''e', so it would appear that Huch is being considered plural. On the other hand, the sentence erroneously has yIvoqQo' instead of tIvoqQo', so I suspect the consideration of plurality was not high here. As data, this sentence is suspect.

Unfortunately, so far as I know, that's the only other time the word has been used in a sentence.

I personally assume that Huch is a mass noun, because money is a mass noun and no attempt has been made to distinguish the grammar of Huch from the grammar of money. That would mean the correct sentence would be Huch law' wIghaj.

-- 
SuStel
http://trimboli.name