https://hkmdb.com/db/movies/view.mhtml?id=5755&complete_credits=1&display_set=eng

I believe this should be "Crazy Bumpkins in Singapore", as it's part of the overall series. Poster confirms this as well.

If no one objects I'll change the title and switch "Crazy Bumpkin in Singapore" to an alias

Agreed. Return of the Crazy Bumpkins has the same issue. No need to keep the incorrect titles as aliases if there is nothing to back them up.