To clarify, if you have a departure ticket at the airport and 20k baht to pay the fine, you won't go to jail, but if you're caught on the street by a police officer and they find out that you overstayed your visa they will arrest you and you'll have to wait an unknown amount of time until you get deported
if you are caught outside of the airport your ban will be 5 years. So your options are a one year ban or a five year ban and a possibility of some jail time while they wait to deport you
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