When does the visa stamp expire if I get it on October 20th after a 30 day exemption in Thailand?

The user is inquiring about the expiration date of their visa stamp after receiving an extension on a 30-day visa exemption and whether they can leave the country before the stamping date without incurring an overstay fine. A comment clarifies that if the 30-day extension is granted from September 27, it will be valid until October 26, and leaving before the stamp date does not incur fines.