while few banks might accept it, most will require a sort of formal bank statement from the bank, something that states that jackfruit got that much cash in his account on that date.
If you apply as a freelancer then the application itself would be far more complicated but u got the advantage that it'd cost you nothing besides of the visa fee. If you apply for muay thai then you have to put in mind that those gyms who offer the dtv documents tend to be way more expensive than those that don't. Nowadays you need to get a 6months course which isn't any cheap and you'll be tied up with that gym for all the time. If you already had your visa through work, you'd have the flexibility of getting to whatever gym u like, as long as u want and u could get better deals/prices. At this point it's your call ;)
I applied for true money when I already had my DTV visa. Sent a picture with the entry stamp and a picture of my visa (the one which got sent by mail by the embassy). Got full access to true money with that (full access for foreigners, can't buy insurance or get access to the financial area)
well, I believe there should be a reasonable amount of money goin into your account. If you got pay a total of 150$ in the past 3 months then it might look suspecious