What I find very interesting is that " patloon" is a feminine word in hindi, when in arabic or even french it is masculine word, my guess is that in western and arab society, pants are worn primary by men, and i India it is part of the traditional outfits for men and women.
Yes it is singular. That a pair of pants, glasses, binoculars, tweezers, pliers, etc are always plural is really an English thing. I believe few or no other languages have this feature