As I mentioned, not sure if it's a requirement Thailand ask to go back to the realm. It's for sure a requirement inside Thailand when your old passport is cancelled and you got a new one, you must transfer your immigration files to your new passport.
That's how it works with US visas, but not sure for Thailand. Most countries of the world want you to transfer long validity visas to your new passport.
Embassy is the only office outside of Thailand able to put the re-entry stamp to the new passport or give you the correct guidelines. Call them and ask for the procedure.