I think it’s not true what you are talking about. The rules about financial requirements just like this:
(a) Applicants must have money deposited in Thai bank located in Thailand with the amount of not less than 3 million Baht; or
(b) Applicants must have money deposited in Thai bank located in Thailand with the amount of not less than 1.8 million Baht and have income with the amount of not less than 1.2 million Baht per year. Once the applicants enter Thailand, they must have accumulated money deposited in Thai bank located in Thailand not less than 3 million Baht within 1 year.
The money in (a) and (b) must be kept in bank account at least 1 year before withdrawing and, within another next year, the money must be left in the account with the amount of not less than 1.5 million Baht and can only be spent in Thailand.
If you don’t want to visit everytime the immigration office before you leave Thailand it’s worthy to apply for a „Multiple Re-entry Permit“. It cost 3.500 THB.
You were lucky just to pay a fine. Many countries in the world put you into jail if you overstay such a period. And by the way, if you not agree the rules of Thailand, just stay away.