Good be much better if doing for the non-o via the evisa system before you arrive. You'll then have 30 days to open a bank account and deposit the 800k. Much easier process than applying after you arrive.
You be better served leaving and applying for your non-o outside Thailand. You might want to consider being on retirement of you're old enough. Marriage has a lot more paperwork and it's a hassle every year.
maybe, have to check your policy for restrictions on it if country coverage. Some don't offer it and others require t you too pay and they reimburse if they approve.