Home Postcode finder WA William Bay William Bay postcode WA William Bay is a locality in Western Australia covered by postcode 6333. Postcode 6333 State or territory Western Australia (WA) Region Wa Subs 2 Gsr Add a free William Bay business listing Be the first listing in William Bay Common questionsWhat is the postcode for William Bay?William Bay, WA has the postcode 6333.What state is William Bay in?William Bay is in Western Australia (WA).Does postcode 6333 cover more than one suburb?Yes. Postcode 6333 covers 17 localities, so the postcode alone does not identify William Bay. Browse other postcodes in Western Australia, or widen the search to every Australian postcode.