No need revoke citizenship cos citizenship granted to the fictitious person name and not original name. The original guy still Pakistan citizen. Imprision to maximum sentence, then deport back and don't allow to transit through SG.
If he got dotters and they chiobu, then can give chance for the kids to stay in SG w/ mother (if she Sinkie citizen)
This guy with 2 names and 2 citizenship can go back Pakistan. Also, since CPF probably to fictitious name, can absorb also.