Kostyuk overcame 10 double faults by converting six of 14 break points in the 78-minute victory. Her second-round opponent in the WTA 500 event will be Britain's Heather Watson, a 6-4, 6-4 winner of China's Jia-Jing Lu.
Seventh seed Ekaterina Alexandrova of Russia held off Varvara Lepchenko 7-5, 3-6, 6-0 and No. 8 Yue Yuan of China rallied past Romania's Elena-Gabriela Ruse 4-6, 6-2, 6-2. Also advancing were Canada's Carol Zhao and Russia's Veronika Kudermetova.
Thailand Open
No. 2 seed Katerina Siniakova of the Czech Republic defeated Australia's Arina Rodionova 7-5, 6-1 in first-round action in Hua Hin, Thailand.
Siniakova converted five of six break opportunities and overcame a 4-3 deficit in the opening set to set up a second-round clash with either Nadia Podoroska of Argentina or Ksenia Laskutova of Russia.
No. 5 seed Xiyu Wang defeated Switzerland's Viktorija Golubic 7-5, 6-1 and No. 6 Katie Volynets outlasted Denmark's Clara Tauson 7-6 (2), 4-6, 6-3. Eighth-seeded Varvara Gracheva of France cruised 6-1, 6-4 win over Taylah Preston of Australia. Slovenia's Tamara Zidansek, Germany's Laura Siegemund and Thailand's Lanlana Tararudee also advanced.
