Lara Arruabarrena's Korea Open title defence was ended in the first round by Ekaterina Alexandrova on Monday.
The Spaniard, seeking her first title of 2017, suffered a 6-3 7-5 loss to the world number 75 in Seoul.
Her fellow seeds in action had no such issues, with Sorana Cirstea overcoming Misa Eguchi 6-1 6-3 in just over an hour.
Meanwhile, fifth seed Irina-Camelia Begu overcame a first-set loss against Thailand's Varatchaya Wongteanchai to record a 2-6 6-3 6-3 triumph.
Sara Sorribes Tormo had the better of a back-and-forth encounter with Heather Watson, eventually winning 6-3 0-6 6-1.
Elsewhere in the draw, Luksika Kumkhum defeated Mariana Duque-Marino 3-6 6-4 6-1, Priscilla Hon downed Karolina Muchova 6-1 4-6 6-4 and Katarina Zavatska lost 4-6 6-3 6-1 to Beatriz Haddad Maia.