how to buy apple developer membership outside US?
Why are you trying to register as an Apple Developer in the US? You only need the one Apple ID, so assuming your Apple ID is based in the UAE you should be registering from there.

Regardless of where you're registered you'll still be able to sell your apps in all App Stores.

If the registration process takes you to the US site, you'll find you can click on the US flag icon at the bottom of the screen. This will open up a screen displaying all countries and their flags. You should find that the first grouping is for Africa, Middle East, and India. You can select United Arab Emirates from there.