Coetzee, 30, a triple winner on the circuit, carded eight birdies and a solitary bogey to finish one stroke clear of Dane Thorbjorn Olesen.
Spaniard Jorge Campillo, Li Haotong of China, Italian Matteo Manassero and Bernd Wiesberger of Austria shared third place on 66 while U.S. Masters champion Danny Willett opened with a 69.
Englishman Willett is second in the money list going into the three-tournament Final Series that also includes the Nedbank Challenge in South Africa and the season-ending DP World Tour Championship, Dubai.
Swede Henrik Stenson and Rory McIlroy of Northern Ireland, who are first and third in the money list, have opted to miss the Turkish event.
"I thought my iron play and wedges were spot on (but) I'm still struggling to get consistency and flight off the tee," Willett told reporters.
(Writing by Tony Jimenez, editing by Pritha Sarkar)
