No, you do not need to purchase a separate Lift Pass to access the Sky Waka you only need to purchase a sightseeing ticket.
To join us on the Sky Waka Gondola, located at Whakapapa ski area, for a sightseeing trip you would need to purchase either a Weekday or Weekend Sightseeing ticket. You do not need to purchase any other Lift Pass to ride the Sky Waka for sightseeing.
Check out this link >>here<< for further information