The German, ranked 464th in the world and on his first full year on the tour, finished four shots clear of the field after shooting a final round 64 for a total of 264.
Home golfers Hennie du Plessis (26) and Zander Lombard (28) finished second on 268 with Scotland’s Ewen Ferguson (28) and South Africa’s Ockie Strydom (38) one shot further back in a tie for fourth.
Bachem hit eight birdies in a faultless round as the other contenders wilted in the final straight.
He went into the tournament testing a new driver, had led at the halfway stage of the tournament but was one shot behind compatriot Alexander Knappe (34) after Saturday’s third round.
The overnight leader fell out of contention as he dropped four shots in the space of five holes to slide down the leaderboard and finish tied 13th.
Malaysia's Gavin Green (29) had also been in a share of the lead early on Sunday but was undone by back-to-back double bogeys and tied for sixth place.
