Heather Watson was knocked out of the Seoul Open at the first hurdle as she lost 6-3 0-6 6-1 to Sara Sorribes Tormo.
Watson, who had moved back into the top 100 after reaching the third round at Wimbledon, has now failed to get past the first round in Korea in four attempts.
Sorribes Tormo, ranked 14 places lower than Watson, broke serve four times in the final set to advance after one hour and 36 minutes.
The Spaniard will now take on third seed Kristyna Pliskova or local wildcard Han Na-lae in the next round.
Elsewhere, Priscilla Hon emerged victorious over Czech Republic's Karolina Muchova after a tight affair which saw the Australian win 6-1 4-6 6-4.
Katarina Zavatska beat Brazil's Beatriz Hadda Maia 4-6 6-3 3-0 to reach the second round as well, where she is joined by Luksika Kumkhum and Ekaterina Alexandrova.
Romanian duo Irina-Camelia Begu and Sorana Cirstea also managed to advance through to the second round on Monday after victories over Varatchaya Wongteanchai and Misu Eguchi.
PA Sport contributed to this report.