I provided 3 months applying in Hanoi. Others have gotten through by showing 3 months but only having the 500k for a shorter time. It's possible, but riskier to show less than 3 months. It will depend on the embassy and agent reviewing your paperwork. There is no across the board hard and fast rule bc Thailand just isn't that consistent. But your chances are much better with at least 3 months.
I'm not on platforms apart from the Korean KUG platform. I have a couple of bookers from Ai English and Dialect Zone. The rest are self booked / parent referrals.
the bureaucracy is def a bit much. They don't really know what they're doing, change their minds constantly, and it often seems they really just don't actually want us here. But they sure do want the money. On the flip side there are many advantages for me personally regarding my medical needs and other things, so this is it for me for now unless I eventually find another good fit.
They specifically mentioned that they do this for your first entry with DTV. Beyond that, I don't know and it's at their discretion. Showing 20k baht is a standard ask when entering Thailand, but they don't always ask it. On the first DTV entry however, it seems they do. As far as the 500k goes, it's Thailand; the rules and expectations are often ambiguous and unpredictable and they are in constant flux. The rule today may not be the rule tomorrow.