LOS ANGELES, 27 Jun 2016, (AFP) - The New Zealand teenager has now won 13 times on the Tour before her 20th birthday as she finished with a three-under 68 for a three round score of 196 at the Pinnacle Country Club course.
Morgan Pressel carded a 71 to tie for second with Taiwan's Candie Kung at 199.
World number one Ko went into the par-five 18 with a comfortable four shot lead but tried to lay up with a six-iron and put her ball into the water.
She blasted her next iron over the green but it hit the bottom of the grandstand and bounced back, leaving her with a somewhat tricky downhill putt from off the green. Ko then two putted for the win.
"It is not the greatest way to finish with a six," said Auckland's Ko. "I hit the ball really well on the front nine."
Ko began the final round tied for the lead with American Pressel. But it didn't take long for her to make her presence felt, jumping out to a four-shot lead over the first five holes.
She had just one birdie and two bogeys on the back nine, which she attributed to the heat.
"I felt a little tired going into the back nine. The sun got to me a little," she said.
Ko had fun with the Arkansas crowd as someone gave her a University of Arkansas Razorback hat to wear on number 17, the tournament's loudest and signature hole.
Pressel's chances of victory ended when she made four consecutive bogeys from number 11 to number 14.
Kung shot a 69 thanks to a late hot stretch. After bogeying two of the first four holes, she was mistake-free the rest of the way, making four birdies, including consecutive birdies on the last two holes.
Angela Stanford (65), Thailand's Moriya Jutanugarn (68), Germany's Sandra Gal (69) and China's Yan Jing (70) tied for fourth at 200.
Sydnee Michaels (64), Australia's Min-Jee Lee (67), South Korea's Yoo Sun-Young (68), Italy's Giulia Molinaro (70) and Canada's Alena Sharp (71) shared eighth place at 201.
World number two Ariya Jutanugarn of Thailand tied for 44th at 207. She is the only other player besides Ko to record three victories in 2016.
Leading scores after the final round of the LPGA NW Arkansas Championship in Rogers, Arkansas, on Sunday (par-71, USA unless stated):
196 - Lydia Ko (NZL) 66-62-68
199 - Candie Kung (TPE) 64-66-69, Morgan Pressel 65-63-71
200 - Angela Stanford 65-70-65, Moriya Jutanugarn (THA) 66-66-68, Sandra Gal (GER) 65-66-69, Yan Jing (CHN) 65- 65-70
201 - Sydnee Michaels 70-67-64, Min-Jee Lee (AUS) 65-69-67, Yoo Sun-Young (KOR) 65-68-68, Giulia Molinaro 66-65-70, Alena Sharp 65-65-71