Really?
Technically you still have to pay for what you overstayed "outside of prison" and nothing during detention.
Interesting if they apply some "creative approach"
btw, the food in IDC is "uneatable" - either you order with quadruple price or enjoy long fasting. Even in BKK, I guess Phuket is even worse.
Poor sod, he probably said something very "british" like "PHOOK OFF, YOU BASTARD!"