Dear Nabil
Becoming a filler, to avoid withholding tax is easy and simple can be done online.
As all Pakistani living abroad their income is tax exempt and by filling tax return you declare your wealth and issue is only if you declare or wealth which is not white.
if you are based in KSA please
contact me InshaAllah will be able to help yourself so you can do it at your own.
some planning is needed which we can discuss my services are free for you:)