When you return on advance parole, you will be considered a parolee, from an immigration perspective. you will no longer be considered an H-1B. As such, you will need an EAD. When you enter as a parolee and returns to work with your EAD, you should ask the H.R. people to revise your I-9, Employment Eligibility Verification form to reflect the new basis for your authorization to work. If you decide to file for an extension of your H-1B in the future, with the approval of the extension, you will resume your status as an H-1B. If you decide never to apply to renew or extend your H-1B, then you can continue to work with the EAD until the I-485 is approved.