Yes, self-registration would be a solution, thank you @richard_smith237.
But where is the guarantee that they will not ask for the same documents - such as a work permit or proof of address from the embassy...
https://www.35yontrakan.com/posts/how-to-register-motorcycle-license-plate-online-in-thailand
There is online registration process, but you must have ThaID app (pink cards do not have a QR code that needs to be scanned).
Can you recommend any easy way to register a motorcycle yourself? 🧑✈️ (dealers charge 2,000 baht for it)