@Fra****
check this.
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You get new full days stamp until your visa (sticker) is expired. When you still have valid 'admitted until stay' stamp after visa itself expired, you need to purchase re-entry permit to keep your rest days 'alive'.
From your OP, your visa (sticker) must have been expired May 2020. You need re-entry permit to enter Thailand using your rest of days from your last stamp. That's the reason
@T**
asked that.
If you didn't get re-entry permit BEFORE you left Thailand. It's done. You will need to enter Thailand next time on another visa or visa exempt entry.