By Lerpong Amsa-ngiam
The 2017 finalist dug deep after conceding the first game to the former world No 1, showing stronger stamina to win their marathon battle in 68 minutes.
“Saina is renowned for her competitive nature, so I just tried to stay with her in the rallies. If she didn’t miss it, I wouldn’t miss. It was a really long match,” said a delighted Busanan, one of three Thais still in the women’s singles draw.
The others are Ratchanbok Intanon, who tamed Germany’s Yvonne Li 21-11 21-15, and unfancied Supanida Katehong who beat Evgeniya Kosetskaya of Russia 21-16 21-8.
“I give her credit for trying to chase down all those shots, but I played better at key points,” said Ratchanok, who lined up a clash against An SeYoung of South Korea on Friday.
Fifth-seeded Carolina Marin of Spain also advanced after settling an old score with Thailand’s Pornpawee Chochuwong 21-8 21-12.
The Spanish world No 6 avenged a heart-breaking home loss in the Barcelona Masters final in February last year with a 34-minute demolition of Pornpawee.
“I lost my last match to Pornpawee at the Barcelona Spain Masters, but that was a completely different situation [after] my father's accident,” said the lefthanded Spaniard, a three-time world champion.
“I played there because it was in Spain and the people wanted to watch me. Now I feel much better and ready for this tournament,” added the fifth seed, who is targeting at least one title from the three BWF events taking place in Thailand until January 31.
Earlier on Thursday, world No 1 and top seed Tai Tzu Ying of Taiwan booked his quarter-final berth by storming past South Korean Kim Ga Eun 21-16 21-10 in just 29 minutes.
"I felt better today and had less unforced errors compared to yesterday. It has been a while since the last tournament, and this is the same for everyone, so [these first few matches] are not easy,” said Tai, who won the All England Championship last March – the final tournament before world badminton entered 10 months of Covid-19 hibernation.
While Thai women triumphed on Thursday, it was a completely different story for their male compatriots. All three – Kantaphon Wangcharoen, Kosit Phetpradab and Kunlawut Vitidsarn – crashed out in straight games.
Booking quarter-final slots at their expense were tournament favourites Chou Tien Chen of Taiwan (world No 2), Denmark’s former world No 1 and ex-world champ Viktor Axelsen, and Asian Games gold medalist Jonatan Christie of Indonesia.
In the mixed doubles, top pair Dechapol Puavaranukroh and Sapsiree Taerattanachai shrugged off a first-game loss to beat Malaysia’s world No 12 Goh Soon Huat and Lai Shevon Jemie 20-22, 21-18, 21-12.