No. If you sign up for a Six Flags Membership you do not need a Season Pass.
Even the lowest level of Membership (Gold Plus) comes with the same discounts Season Pass Holders get. In addition, Members come with a lot more benefits that aren’t available on any of our Season Passes. If you’re looking for the best experience with the most discounts, the best value, and the most unique experiences, a Membership is likely for you.