No.1 seed Bianca Andreescu powered into her first semifinal since last June with a 6-0, 7-6(3) victory over No.5 seed Marta Kostyuk at the Thailand Open presented by E@.

The quarterfinal clash was a matchup of the 2017 Australian Open junior champions. That year had seen Kostyuk take the girls' singles crown; Andreescu had fallen in the singles semifinals, but captured the doubles title alongside Carson Branstine.

Despite being junior peers, this was the first time the pair had played at any level. Andreescu, the 2019 US Open champion, dominated for a set and a half, taking on the ball at every opportunity and racing to a 6-0, 5-1 lead.

But Kostyuk fought back to win the next five games in a row, saving triple match point serving at 3-5, and Andreescu ultimately needed a tiebreak to get over the line.

"I think I played really well, especially in the first set," said Andreescu. "I don't think I played bad in the second set -- she just raised her level."

More Hua Hin highlights: Zhu d. Wang Xiyu, R1 | Maria d. Eala, R1 | Watson d. Putintseva, R1 | Kostyuk d. Liang, R1 | Zidansek d. L.Fruhvirtova, R2 | Andreescu d. Zakharova, R2 | Wang Xinyu d. Watson, QF | Tsurenko d. Maria, QF

Andreescu will next face former World No.23 Lesia Tsurenko, who made the last four after a patient 6-1, 6-1 defeat of No.6 seed Tatjana Maria. The result put the Ukrainian into her first tour-level semifinal since reaching the 2018 Brisbane final.

There will be an all-Chinese semifinal in the bottom half of the draw after Zhu Lin defeated Tamara Zidansek -- though not before Zidansek thrilled the crowd with a hot shot -- and Wang Xinyu overcame Heather Watson