Sorry for the loss . But they will let you leave but just don't get caught in between. That's where the problem will lay if you get caught by police between now and the airport ...
You will probably be barred for 5 yrs and pay 20,000baht fine. But just don't get caught between now and the airport otherwise you will be taken to IDC . But in your situation with the courts you might be ok at immigration.
Not all currency exchange places are rorts. I came 2 weeks ago got 1000 Aud worth at 23.34 baht to the dollar which at the time the going rate was 23. 65 baht. Not at the airport either .
What's it worth to you .?1900 baht fir an extension or get an overstay stamp in your passport and 1000 baht fine and running the risk of denied entry next time