Campbell hit a four-under-par 66 to finish 19-under and pip Smith to a title previously won by major champions Rory McIlroy, Justin Rose and Greg Norman, with overnight leader Phachara Khongwatmai suffering a late slump to drop into a tie for third.
"I was battling away all day," said Campbell, who becomes the first player to win the tournament since its return from a four-year hiatus due to the COVID-19 pandemic.
"I didn't get off to the best of starts and the swing wasn't feeling that great.
"I was getting a bit tight in the swing but from past experiences, I was able to put together a couple of nice swings down the stretch, which really helped."
Phachara led Smith by a shot with Campbell a further stroke back when the final trio stood on the 16th tee, but the Thai's drive deep into the bushes resulted in a double bogey that dropped him into a share for second with Campbell.
However, a birdie at the next for Phachara and Campbell, who both sunk six-foot putts, meant the three players went to the final hole level on 18-under.
Campbell prevailed, rolling in a perfectly judged downhill putt to win by a stroke from Smith, while Phachara's bogey saw him finish in a tie for third with Canada's Richard Lee.
"I hit a few putts there in the practice round so I knew what I was doing," said Campbell.
"I knew I was just going to aim and let it fade in there. It's always nice to pull off the shot. Doing it under pressure's another thing."
