كيف يمكن الإبلاغ عن شخص في السعودية عليه دين مستحق لبنك في دبي؟

Easy, Dear Questioner,

You can proceed against him inside the UAE with a case, and once you receive a final verdict, you can attest it and sue him in KSA with the final verdict.

We are in the GCC. UAE and KSA are part of the GCC, meaning to say whatever happens here can be enforced at any of the GCC countries if you followed the regulations in this regard.