You can only get a Non O-A visa in your home country. You cannot get it in Thailand.
You can get a Non O visa ‘for Retirement’ in Thailand, which is probably better anyway as no compulsory Health Insurance is required for each Extension.
Both visas allow you to stay in Thailand permanently if you wish.
You need to specify the type of visa. A Non O for ‘Retirement’ or marriage etc is a 90 day visa which you can get inside Thailand. If you mean a Tourist Visa, which is 60 days but can be extended for another 30, then no you can’t get it in Thailand. You could apply online for future use, but you can’t just activate it inside Thailand. You’ll need to show a flight and it must be used at a border.
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.
In late April or early May use the online system to get a Tourist Visa. You’ll have 3 months to use it so will be fine for 10 July. You’ll then get 60 days on entry which you can extend for a further 30 days at an Immigration office in Thailand.
You could start by joining the ‘Jomtien Complex’ and ‘Supertown Jomtien Complex’ groups on FB. They are both run by business owners in the Complex - which is an area in Jomtien with restaurants and gay bars. The area is popular with a lot of people whether gay, straight, male, female etc.
To use the evisa system you’d have to show proof of residency in Spain. You could try applying to the London embassy online but they’ll want to see flights. If you provide a flight to Spain and then a flight from Spain to Thailand you ‘might’ be ok but I’m not sure.