Keothavong crashes out in Kuala Lumpur
Taiwan’s world number 123 was a break down in the second set but broke back before winning the last two games en route to victory over the Londoner, ranked 44 places above her and seeded eighth for this tournament.
The next three seeds all progressed on Tuesday but needed three sets to do so.
Second seed Jelena Jankovic needed two tie-breaks to get the better of France's Caroline Garcia 7-6(7) 4-6 7-6(2).
In other results, Czech Karolina Pliskova beat Chang Kai-Chen of Taiwan 6-3 6-2, Eleni Daniilidou of Greece beat Sania Mirza of India 6-2 1-6 6-4, Kristyna Pliskova of Czech Republic beat France's Iryna Bremond 6-0 6-2, American Jill Craybas beat Japan’s Yurika Sema 6-4 1-6 6-4, and Casey Dellacqua of Australia beat Serbia’s Bojana Jovanovski 6-0 6-2.