When manufacturing necklaces, chokers etc..., if you put the necklace
the correct way around the neck, is the chain(clasp or lock) supposed
to be hang from the right or left hand side?

Here in the UK it is clasp on right for male and on left for female..

Tuneman?©® "Bling Bling Expert"

..same as button differences for men and women on clothes

Since most people have better finger coordination with their right
hands, it seems to me that it would make sense to place the clasp in
such a way that it would be on the wearer's right.