Question about annual new car bureaucracy

I bought a truck new last June in Bangkok. Due to trips outside Thailand I didn't get a 90-day report to get a residence certificate to register the truck at DLT. (My UK embassy doesn't do res cert so I needed the TM47.)

When my truck is a year old, I'll have to pay tax and insurance (anything else?)

Do I need to register the truck before I can pay the tax?

Do I have to register the truck where the showroom is? Or can I contact Ford in Hua Hin?

Is it lots of work to move a vehicle registration eg from HH to Bkk?

My last 90-day was Bkk, but I'm living in HH and my 90 day is due in a few weeks.

Huge thanks