If you are applying for only a tourism extension, it wouldn't be a problem. You can apply for it as normal.
If you are going to apply for any long-term visa/extension, it might be an issue. You may need to apply for a cancellation old extension before you are able to do so, and in the worst case it could be a
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baht fine, but no other penalty. It's the old extension, maybe the best way is going to go to the immigration office and ask them about what you should do.