@Mike **********
If you can get a Non-O approval before you arrive its a bit like a golden ticket .
Of course there are requirements .
Once you are here you need to fairly quickly open a Thai bank account &
Deposit 800,000 baht in it & leave it sit for a minimum of 60 days.
Proof of address here
Some immigration offices may want more evidence, others may not
If it all seems difficult you can hire a Visa agent to assist