Craig had five birdies -- four on par 4s -- on the second nine en route to his 65 on the East Course of the Royal Johannesburg and Kensington Golf Club.
Each player in the field of 210 plays the East and West courses once either Thursday or Friday. The tournament moves completely to the East Course for the final two rounds.
Eight more players are at 6-under. James Hearth is the only player in that group who played the East Course in the first round. A crowd of 12 players, including defending champion Richard Sterne, is at 5-under.
Forsyth was 6-under in the first nine holes Thursday and ended the day without a bogey. Molinari and Walters both had bogeys at No. 4 against eight birdies.
Craig made the turn at 3-under before twice getting back-to-back birdies -- at 10 and 11 and then at 14 and 15 -- on par-4 holes. His only bogey of the day came at 17 but he returned to a share of the lead with an 18th-hole birdie.