Ukrainian world No.4 Svitolina, who dispatched Australian qualifier Storm Sanders in the previous round, slumped 6-2 6-4 to Japan's Nao Hibino, ranked 80 places below her, on Friday.

"I'm so happy to win the match today because she's one of the top players in the world," said Hibino, who had never previously beaten a top five player.

"I've been watching her on TV so many times so I'm so happy. I love playing here in Thailand so I want to stay as long as possible."

Hibino took control of the match in the opening set and continued her dominance in the second to secure victory in one hour and 18 minutes, leaving Svitolina to admit she lost to a better player.

"It was very hard conditions to play and to be fair she played a great match, she went for it on important points and got rewarded for it," the 2018 WTA Finals champion said.

"I wish I could play a little bit better on the first set, and I think this was the key, and she played really unbelievably at the important moments."

Another upset saw 19-year-old Swiss qualifier Leonie Kung power into the semi-finals in just her second WTA Tour main draw event after defeating third seed Wang Qiang of China 7-5 4-6 6-4.

Polish fifth seed Magda Linette fought back from a set down to beat the youngest player in the draw, China's 18 year-old Xiyu Wang.

She will now face Romanian Patricia Maria Tig in the last four, who battled past fourth-seeded Chinese Saisai Zheng.

Australian Associated Press