Former world No. 1 Ana Ivanovic started her first-round match on Tuesday and finally lost it on Thursday at the rain-plagued Pattaya Open.
Two-time defending champion Daniela Hantuchova also exited the draw on Day 4.
The top-seeded Ivanovic succumbed to Japan's Ayumi Morita 6-3, 5-7, 6-3 in a match that was suspended on Tuesday, and washed out on Wednesday, with Morita leading 2-1 in the third set.
The sixth-seeded Hantuchova, meanwhile, saw double duty on Thursday, as the Slovakian veteran got past Belarusian Olga Puchkova 6-1, 3-6, 6-0 in a first- round affair before losing to Russian Nina Bratchikova 6-2, 3-0 in the second round, as Hantuchova retired against Bratchikova at this hardcourt event.
Hantuchova beat Russian glamour girl Maria Kirilenko in last year's Pattaya finale.
A second-seeded Kirilenko avoided a second-round upset Thursday by overcoming Thai wild card Luksika Kumkhum 5-7, 6-2, 6-2.
Another Day-4 upset came when Latvian qualifier Anastasija Sevastova upended eighth-seeded Brit Heather Watson 7-6 (7-4), 4-6, 6-2 in a second-round affair.
In other second-round action involving seeds, No. 4 Romanian Sorana Cirstea topped Aussie qualifier Anastasia Rodionova 6-0, 7-6 (7-3), No. 5 German Sabine Lisicki doused Russian Alexandra Panova 7-5, 6-2, and No. 7 Russian Elena Vesnina held off France's Mathilde Johansson 6-2, 3-6, 6-1 in her second match of the day. Vesnina opened her day with a 6-2, 5-7, 6-2 first-round victory over Greek Eleni Daniilidou.
In other second-round play, New Zealand's Marina Erakovic bested Thai wild card Varatchaya Wongteanchai 6-3, 7-6 (7-4) and a busy Morita took out 42- year-old fellow Japanese Kimiko Date-Krumm 4-6, 6-4, 6-1.
Friday's quarterfinals will pit Kirilenko against her fellow Russian Vesnina, Cirstea versus Sevastova, Lisicki against Erakovic, and Morita versus Bratchikova.