Both were the only Thai winners in the Friday’s quarter-final programme. Seventh-seeded Boonsak needed 58 minutes to eliminate RMV Gurusaidutt 21-12 11-21 21-12 while third-seeded Ratchanok came back from a first game down to pick off Arundhati Pantawane 14-21 21-7 21-16 after a 53-minute battle.
There was no luck for Ratchanok’s countrywoman Nichaon Jindapon as she squandered a first-game win to hand the match to Indonesian Aprilla Yuswandari 21-18 16-21 18-21.
In the doubles quarter-finals, Maneepong Jongjit and Nipitphon Puangpuapech lost to third-seeded Sung Hyun Ko and Yong Dae Lee of South Korea 20-22 19-21.
Duanganong Aroonkesorn and Kunchala Voravichitchaikul lost a tough battle to fourth-seeded Miyuki Maeda and Satoko Suetsuna of Japan 13-21 17-29 in the women’s doubles, while former world No 1 Sudket Prapakamol and Saralee Thoungthongkam were upset by Chris Adcock and Gabrielle White of England 21-19 11-21 15-21 in the mixed doubles.
World No 1 Lee Chong Wei of Malaysia stormed into the men’s singles semi-finals with a 21-14 21-19 victory over India’s HS Prannoy.
The Malaysian will now take on Boonsak.
Top-seeded Lee, who clinched the opening game comfortably, faced some anxious moments in the second when he trailed 18-12 before asserting his supremacy in the 34-minute encounter.
The other men’s singles semi-finalists were sixth-seeded Japanese Kenichi Tago and Anand Pawar of India. The Japanese overcame India’s Sai Praneeth 21-17 19-21 21-11 while Pawar downed compatriot Ajay Jayaram 21-6 21-16.
Indian teenager PV Sindhu, seeded eighth, moved into the women’s singles semi-finals with a 21-16 21-16 victory over Japan’s Yui Hashimoto.
Sindhu, 17, will now clash with Ratchanok.