After over a decade of living in Thailand under my belt, I have to say this question has been coming up for years from people who have just realized they have overstayed their visa and are worried about it. Many expats and tourists do not know the correct answer to it, but they will try to convince you that they do.
“Will I be charged a 500 baht fine if I have a one day overstay in Thailand on my passport, and am planning on leaving the country on my first day of overstay?”
And it comes up a lot because there has been a rumor going around in the expat community for years that, no matter how long your overstay is, you will be charged a 500 baht fine for every day you overstay. Starting from the first day.
Sorry, but that is not true. Because here is what you really need to know about the 500 baht per day overstay charge levied in Thailand.
Leaving Thailand from an airport
If you look at your passport and realize the day you are leaving Thailand is actually the day after your visa expires, as long as you leave on that day and from an airport, you will not be charged for a one day overstay. Nor will your passport be stamped with an overstay stamp.
If you leave Thailand two days after your visa expires, even if it is going through immigration at the airport one minute after midnight on the second day of your overstay, you will be charged 500 baht for the second day overstay, and you will get an overstay stamp put into your passport. But you will still have no charge levied for the first day of overstay.
This, however, is only if you are leaving Thailand via an airport.
If you leave Thailand by a land border
The minute your Thailand visa expires, so does your permission to stay and especially if you leave Thailand by a land border.
That means, if you leave Thailand via Laos, Cambodia, Myanmar or Vietnam, and via a land border, you will be charged 500 baht per day from the first day you are on overstay. And your passport will also be stamped with an overstay stamp.
This is why, if you made a mistake when it comes to the day your Thailand visa expires, you are better leaving Thailand from an airport rather than via a land border.
From an airport, you will not incur any fine on the first day after your visa expires, neither will you get an overstay stamp applied to your passport. From a land border, you will get both.
It has always been this way, and I am guessing it will likely always be this way. I hope that is clear.