In a flashback scene when little Noi is making funny faces to little Sai, it's shown that his hands are on his face but in the next shot it's not, this continues until the scene ends.
When Noi sees a Krasue, his hands are dirty with mud on them. When he chases after the krasue, his hands are clean.
When Sai is cleaning up the wound, it is shown that her hair is covering her ears. In the next shot her ear is shown.
When Sai transforms to a krasue at the movie theatre, when her headless body is shown, there is a head, in the next shot.
When Sai transforms for the first time, her eye moves but her other eye doesn't move. This happens for a few seconds.
When Sai fully transforms at the movie theatre, her eyebrows are not shown.