You can either get your initial Non O Visa in the USA or enter on a Tourist Visa, or even Visa Exempt, and get the Non O in Thailand.
That gives you 3 months before you need your first Annual Extension.
For your first Extension you will have to show the 800k in a Thai bank account for at least 2 months.
For future Extensions you could use income but you must send at least 65k from overseas to your Thai bank account every single month without fail all year.
You can combine income and bank balance but again must show it every single month for a year.
Some offices insist on proof the money sent is from a pension.
You are not allowed to work on a Retirement Visa so don’t tell them (or anyone) you are running an online business.
If you can’t do this the alternative is to pay an agent which will cost you about
*****
baht for the initial 15 months then about
*****
baht or so each year after that. It depends if you are comfortable doing this. Many people use them, others do not want to.
As for the new tax laws, no one knows yet how, or even if, they will be enforced and probably won’t know until 2025.
If they do enforce them as written then it could be an issue for lots of people, especially those sending money each month, but as I said NO ONE KNOWS YET.