You realize that 1) insurance coverage is not required for non-o based on retirement visa. 2) healthcare is at least ⅓ the cost of haha in USA and its in many ways better quality.
Suggest you get retirement visa while abroad. Makes whole process much easier. Maintain USA bank and investment accounts and transfer money as needed. Your money will earn a lot more there than here and it is much safer. Suggest retirement versus marriage. Less paperwork and lower risk if for some reason your marriage didn't work out in the future.
I've not heard of anyone being declined a bank account here in hua Hin who have a valid non-o, a residency certificate and copies of their passport pages ... Don't know where you're located, but Bangkok bank here is quite accommodating. I'm told (but don't know from experience) that immigration will issue a letter to the bank if you request it at the time of obtaining your residency certificate. What type of visa are you on?
because of the financial requirements of those visas and because Thailand wants their residents to keep their money in ฿.
Things have gotten tighter to clamp down in money laundering. Bank accounts that sit idle for looking periods are ripe for identity their and fraud because no one is looking at them.