@Tod ********
that’s wrong . You get overstay as soon as you visa expire so if you visa expire on 10 January for example and you show up at the airport the 11 January at 2am tou will be fined 500thb ( already happen to me for less than 1h past the due date. The only time you wont get fines is if you apply for an extension and your last day is a sunday , immigration are closed on saturday and sunday so some of them won’t charge you the overstay but will still put the stamp on the passport.