The 23-year-old Moriya’s win by two strokes means that the Bangkok siblings join Annika and Charlotta Sorenstam as the only sisters to win on the USLPGA Tour.
Moriya was at a loss for words as she celebrated the win on the 18th green of the Wilshire Country Club with her family members and friends.
“My sister is crying more than me,” said Moriya as she wiped tears of joy. “I can’t tell you what I feel right now.”
Ariya, 22, watched the final putt drop from just off the green as she stood with her arm around their mother. When Moriya sank her putt to reach a 12-under 272 total, Ariya skipped onto the green and shared a long emotional hug with her older sister.
“It feels great,” said Moriya. “I had a lot of patience out there. Finally my week comes through. I had a pretty solid weekend and I am pretty happy with that.”
Park In-bee, who will return to the No.1 ranking in the world today, shot a 68 to finish in a tie with fellow Korean Ko Jin-young who had a 70.
Ryu So-yeon finished alone in fourth at seven-under 277, five strokes adrift of Moriya.
Ji Eun-hee shot a 71 and tied for fifth with Emma Talley as four of the top six players were from South Korea to the delight of the large Korean expat crowd that was in attendance.
But the day belonged to Moriya, who won on her 156th start and was joined in celebration by another Thai, Sherman Santiwiwatthanaphong, who shot a 69 and finished in a season-best ninth place.
Former world No.1 Ariya has been the conquering hero over the past two years, becoming the first player from Thailand to win a major championship when she claimed the 2016 British Open.
Even before today’s win, Moriya put her own stamp on the Tour, winning the rookie of the year award six years ago.
Today Moriya turned up the heat on the back nine, making birdies on four holes beginning at the par-three 12th. Her only blemish of the day was a bogey on 16, but she recovered to par the final two holes.
Seven time major champion Park is poised to regain the world No.1 spot when the rankings come out today. World number three Park needed to finish in the top six and have current No.1 Feng Shanshan of China place where she did in a tie for 12th.