Yes, a Discover Pass is required for vehicle access to Washington state parks, including those with camping facilities. The Discover Pass is a permit that allows you to visit and park at Washington state parks and recreation lands managed by the Washington State Parks and Recreation Commission, the Washington Department of Fish and Wildlife, and the Washington State Department of Natural Resources. However, the pass does not cover camping fees, which are separate and vary depending on the park and type of campsite. You can purchase a Discover Pass online, at any state park, or at various retail locations. The annual pass is $35, and a one-day pass is $11.50.
For more information on camping in Washington state parks, check out Hipcamp.