Perfect net shots on both sides. It seems that Ratchanok racket had crossed over the net line on the last hit, and it’s not a fault. The reason is because you can hit the shuttle after it cross over to your side and you are allowed to finish your stroke on the other side of your opponent court.
It is stated in the Official Badminton Rule book section 13.4.2:
“It shall be a ‘fault’: if, in play, a player: invades an opponent’s court over the net with racket or person except that the striker may follow the shuttle over the net with the racket in the course of a stroke after the initial point of contact with the shuttle is on the striker’s side of the net;”
You can read it here “Laws of Badminton“