I say a month only because if you only spend a day or 2 then return on visa exempt, you will 1. Not have time to get a visa, and 2. It is the short trips that will start people asking questions quicker.
You may have to have a 2nd place besides Thailand that you can spend a month at, in between Thailand visas and extensions. (Or be a true tourist in between visas). But I think it will get hard if you are not moving about Thailand as well.
As Stuart says, Yes, come in on visa exempt. Book a short flight to Kuala Lumpur to satisfy the proof of onward travel within the initial 30 days. If your visa doesn't come through, you will either have to leave the country for a few days (go to Kuala Lumpur etc) or get an extension at Immigration.
I am actually confused as to what you are asking. Are you trying to go to some sort of school, or are you just trying to extend your stay as long as you can?
I would come in on a 60 day tourist visa, extend 30 days, then just do a couple of border bounces, spending a few days exploring nearby countries each time, then return visa exempt (Which you can extend 30 days as well.)
This thread has hurt my head. 🤣 So, the visa has expired, so you need to start over with 800,000 in the account, whenever or however you can get that. Wouldn't you need to leave the country for a bit?
A border bounce is just getting a new stamp in your passport. Usually for exempt entry. Or maybe a multi entry visa where you have to leave every 90 days. If you are renewing a visa, you are planning to spend a few days working this process in another country. Then you come back on your new visa.