Ratchanok started with a 3-1 lead but a string of unforced errors came from her racquet which saw her lose the opening game 13-21 in just 19 minutes.
In the second game, Ratchanok raised the level of her game and rallied from 12-17 to draw level at 19 all with the world No 4. But the more experienced Wang who earlier had beaten the Thai seven times in a row dictated the next two points to seal off the victory after 46 minutes.