Yes, 1 day = 500 baht.

@Benjamin *****

the agency cancelled my work permit on the 11th April, but I found it out only at the beginning of May. I went to Chonburi immigration office and they said you can use it. Yes, that was an extension. I crossed the border with Laos twice and no one saw that as a problem. Then I found job at another school and I got new NonB visa. But only when we went to extend it in Samut Prakan Immigration, they found those 43 days...

I had to pay 20,000 baht for 43 days overstay, because they count from the day the Work Permit is cancelled. It was the same - the visa wasn't cancelled by the employer. But the work permit was.