The dragon is a standard fold until you come to the head and neck. At this point there is a "secret" extra fold upwards in the dragon's front arms that makes the upwards fold of the neck possible. The base of the neck can then fold back in on itself, I wish I could post pictures but I managed to replicate it after many ruined pieces of paper. 😅
There is a secret fold back upwards in the front arm that makes the neck bend upwards possible. It is impossible to see the fold in the video, that's why I call it "secret" but once you get that crease in the whole thing becomes possible! 😅