34-year-old Purkiss, who has been without a club since leaving Swindon Town at the end of last season, is looking to step up his rehabilitation from a neck injury that has sidelined him since the summer.
While he continues his rehabilitation, Ben, who is Chairman of the PFA, will assist in opposition analysis and provide support for the younger players at the club, something he is looking forward to.
Speaking via the club's official website - Saddlers.co.uk - Ben said; "I’m delighted to be back. Walsall are a club close to my heart and I’m grateful of the opportunity they have afforded me.
"While I’m not putting a timescale on my return, I’m hopeful of recovering from my neck injury and believe I still have a role to play at the club, both on and off the field."