A retirement visa is very different, its actually designed to allow you to spend the rest of your life in Thailand should you so choose without ever having to leave. It in no way resembles a tourist visa. You can't stay a year inside Thailand with the DTV, even if you can find an IO that will give you an extension the absolute longest you can stay is 360 days then you have no choice but to leave. Do you really think the fact you can't get a full 12 months out of a DTV (even with an extension) is some sort of error?
not downgrading anything. Just stating a fact. The DTV is classed as a tourist visa. And as such carries the same restrictions as any tourist visa does.
There's a reason you can't stay for even 1 complete year inside Thailand on a DTV (if you are able to get an extension). And that's to distinguish it from visas that do allow you to establish a life in Thailand without ever having to leave.
It's not that the situation has changed but they have got stricter about enforcement. A visa exempt entry is for tourism and you are not a tourist, saying that only the immigration officer you will stand in front of can answer your question. If you are worried about it you can get a 90 day Non-O based on your marriage rather than trying visa exempt
The 800k baht must be in an instantly accessible account. It doesn't rule out fixed deposits as some will allow you to withdraw money but you pay a penalty such as losing interest etc
Have your partner write a letter signed by the company boss explicitly giving you permission to work remotely from Thailand. It would also be worth including that you will not work with any thai clients or entities