I returned with a 60 day tourist visa when it happened to me been in and out for 36 years only asked once! A friend who had the same problem and ignored it was deported on arrival!
Your fist move is to look up your local Thai 🇹🇭 Embassy and read the Visa requirements on the visa application page, this will give you a good idea of what you will need .
Depending on your Passport country of origin ( where you live) you can get Visa exemption for 60 days on arrival and this can be extended by 30 days at your local immigration office, however if you want or need a ‘Visa’ this needs to be applied for (mostly online) in advance
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