Keep your 800k in place and then work to send your money in from offshore (carefully so that it is shown as money from outside the country and for the visa).
Some of the money transfer companies can do this.
Although sometimes it glitches so if you can have an extra month ready to go so you can keep the monthly points hit. If you have to recycle a bad transaction so that it goes out but then comes back in, for the documentation.
This presumes a lot and you said you couldn't verify it, so this may be a way to build up a pattern of income you can show later. Then if you are firmly on that you can let the big account be used.
If you can generate money in the US or other country while you are offshore in Thailand then you can have your cash flow.
Getting in now is challenging. I hope that the new vaccine will get things going again.
There is a new visa that is good for 90 days and can be extended twice. This will get you to about
***
of a year.
You can also take a trip to a nearby country to reset your visa clock. Do a lot of research on this as there is a lot of changes in this area.
So, I think there is a bit of waiting before you can go. Use this time to use your sales skills to create an online sales of something. Then when you go it can serve as your income. Research all of the details as best you can. Look at YouTube to get some feet on the ground feedback.