score:10
Per GCMap, the route flies clearly south of Japan's Okinawa island chain, and thus does not enter the ADIZ. Of course actual flight routings will vary from the ideal great circle route, but usually not by much.
(courtesy Great Circle Mapper)
Also, Singapore has stated that they will file flight plans with Chinese authorities. Not entirely sure if this affects all flights to/from Singapore, or just ones operated by Singaporean carriers though.
Also also, I don't see the Chinese shooting down passenger airplanes anytime soon, or even scaring them with fighter jets, it would be really bad PR for China's "peaceful rise".