Date-Krumm, 43, topped Tadeja Majeric 7-6 (7-4), 6-3 for a second win in the tournament over a player at least 20 years younger. Date-Krumm was 0-for-4 in saving break points against Majeric but finished off six break opportunities of her own.
She won 60 percent of the points and piled up four breaks off Majeric's serve in taking the second set.
No. 5-seeded Elena Vesnina won two-thirds of the points on serve in a 6-3, 6-3 decision over local favorite Nicha Lertpitaksinchai. Vesnina had the only break of the first set and then broke Lertpitaksinchai's serve three times in five receiving games of the second.
The final second-round match went to eighth-seeded Peng Shuai, who defeated Alexandra Dulgheru 6-3, 6-4 with a pair of breaks in each set.
Peng meets Andrea Hlavackova and Date-Krumm draws fourth-seeded Ekaterina Makarova in Friday's quarterfinals. Also Friday, Vesnina is to play Julia Goerges and No. 3-seeded Sorana Cirstea goes against Karolina Pliskova.
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