Please Wayne avoid Pataya it’s bloody awful place. Phuket offers everything for a start. Lively if you want it. Quiet and scenic. Good motorcycling roads to the south. It’s a great place to start. I’m in Karon as a base but you can get to anywhere in Thailand from there. I’m still exploring. I’m near vietnam border as we speak. Did Pattaya earlier this year and will never go back.
My friend used an agent and it only took one week. You will have to prove your funding however for the reasons you’ve given and they make a big thing about how long you’ve been together and prove it with photos together etc. he is Italian so same thing really. Hope this helps