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Yang beat her rivals on Pattaya Old Course at the Siam Country Club in Chonburi, Thailand.
The golfer, who joined the LPGA in 2008, first won the title in 2013.
Among other South Koreans in the Thai tour, Kim Sei-young tied for fifth at 12-under and Park In-bee ended another stroke behind in a tie for eighth, Yonhap said.
By Ro Ji-woong (jamesro@heraldcorp.com)