The 19-year-old qualifier who is named Gun by his family had no intimidation playing against the former world No 1 as he stunned the Chinese fifth-seeded 21-15 21-19 in 41 minutes in the BWF World Tour Super 500 event.
"Actually he was hitting shots better but I just fought hard for every point and won the match. I'm so overwhelmed," said Kantaphon.
The 61st ranked teenager who reached the semi-finals of the Thailand Masters two weeks agowill next face Anthony Sinsikuna Ginting of Indonesia on Thursday.