Phatlum was knotted with Karine Icher after 18 holes of the two-round unofficial LPGA Tour event, but used five birdies on the front nine to open up a lead and cruise to a win at Itanhanga Golf Club.
She finished at 13-under 133, four better than Amy Hung (65) at minus-9.
Sharing third at 8-under were Chella Choi (67) and Paula Creamer (69).
Icher stumbled to an even-par 73, ending in a tie for fifth at 7-under.
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