if you have not extend you current visa or visa exampt, you can get a 30 day extension of stay based on being a tourist for 1900THB.
If you already have gotten this extension, then some immigration offices may sell a 7 day extension of stay denied stamp. When you get that stamp, you have 7 days to leave Thailand.
For some nationality, and for some circumstances, your country may issue a letter saying you can not travel due to the COVID-19 virus. If you do, you may get an additional 30 day extension of stay. Talk to your embassy tomorrow. If you are on overstay, you will not get that extension.
See
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for more information about the COVID-19 letter.