As Ryder Cup player Pieters recorded his first title triumph in three years by winning the event for a second time, Johnston handed himself a timely boost after missing six cuts in his previous nine events.
The 26-year-old from Dumfries was one-over after eight holes in the final round at Albatross Golf Resort before transforming his day with a burst of three birdies in four holes as he signed off with a 70 for a 14-under-par 274 total. He picked up around £28,300 to jump 16 spots to 143rd in the Race to Dubai.
Pieters finished on 19-under as he held off a brave late charge from his playing partner Adri Arnaus to win by a shot, repeating his success in 2015. “I’m relieved. It’s been a long time since I won,” said the 27-year-old.
Bob MacIntyre cemented his position in the top 15 in the Race to Dubai by claiming a share of 23rd spot on nine-under, while Scott Jamieson and Richie Ramsay ended on seven and four-under respectively.