The South African birdied four of the last seven holes, including a difficult chip-in on the par-4 12th, to finish at 9-under 135 overall, one shot ahead of Shanshan Feng (67).
“It played a lot tougher than the last few days,” Buhai said. “The wind was more or less the same direction, just a bit stronger, so I think it helps being the same direction as you have an idea what to do. It was just a case of taking more club and just trying to play it with the wind.”
Feng shot the best round of the day with her 67, a score that moved her up 13 places and into second.
“I knew that after the first round, I would be warmed up a little more,” Feng said. “I would say my ball-striking today was better, so I was giving myself birdie chances.”
First round leader Sun Young Yoo (74) dropped to third place at 5 under, while Lizette Salas (73) is fourth at 4 under. Defending champion Minjee Lee (73) is in a tie for 20th at even par, along with No. 1-ranked Sung Hyun Park (76). Alena Sharp of Hamilton, Ont., was at 1 under after a 74.