The 18-year-old American entered the final round with a comfortable three shots lead over Lee Ilhee form South Korea. Thompson had a slow start as she recorded a one above par in the front night, but bounded back strongly by grabbing three consecutive birdies in the 10th, 11th and 12th hole.
She finished the final-round in 69 for and a four-day total of 19-under par 265.
“It got really close. I had a little off start. I had a few bad tee shots. But I was just trying to stay into it and be confident with all my tee shots and shots into the green,” she said.
China’s Feng Shanshan finished four shots behind Thompson to win her second runner-up this season with a solid 4 under par on Sunday, a week after she won her second LPGA title in China.
“I played with Lexi (Thompson) yesterday, she’s in good shape. We know she’s not going to do bad today, so I had to shoot a really low score to catch her, which I tried but I didn’t make,” said Feng.
“But I think 4 under is still a very good round for me,” she added.
Lee Ilhee managed to cut Thompson’s lead to one shot at one point, but failed to catch up later. She tied third with four-round 272 with Suzann Pettersen from Norway.