You don't enter a home country address, just country and state (for GBR = County), or simply use passport country. The address required is your Thai address.
The "health declaration" is only relevant if you have travelled recently to Yellow Fever countries. Hardly a reason to postpone travel plans if you have not.
Maybe they will have "helpers" to check who has or not got their QR code ready, they used to do similar with the TM6. Anyone without can go to a single mile long queue to complete the formalities, the rest of us can sail through unhindered.