The two women battled into the quarter-finals on Thursday, with the 19-year-old Thai coming from behind for the second day in succession and then producing a confessional about her mental state.
At one stage Ratchanok was a game and 11-11 down before getting past Han Li, the world number 19 from China, by 18-21, by 21-14, 21-11.
The day before she was within three points of defeat against the Singaporean Gu Juan.
"Everyone has been trying to beat me and I have been putting myself under pressure and been scared of the losses," said the Thai teenager.
"So I try to concentrate on practising. I try not to think about the world championships because I am not the world number one."
That of course is Li, who earlier made a great escape for the second successive day by coming from a game and 8-13 down against Minatsu Mitani, the world number 16 from Japan, also drifting to within three points of defeat before winning 14-21, 21-19, 21-15.