Don't know about future entrances, but you pay the fine at immigration. But from what I know, you can still do it after a week of deadline. Of course you'll still need to pay fine for not having TM30 as soon as you get back into Thailand.
Same situation. We had to fill up some forms. We had to confirm our residence, job contract, income, National ID/ Driver Licence, Passport, Visa. And they said it'll take probably a week and call us back. As of now, we cannot take out the money, or close the accounts.