How do extension dates and re-entry permits work when leaving Thailand around my visa renewal date?

The individual is planning a trip out of Thailand around the renewal date of their visa extension. They are concerned about whether exiting Thailand in October will result in the new extension date being applied or if the old one will remain in effect. Additionally, they want to know if the re-entry permit will be valid until the new extension date or if it will expire with the current extension. According to a comment, the person can apply for a new extension during the last 45 days before the expiration date. Once the new extension is stamped, it will be valid until the approved date, and they can apply for a re-entry permit to maintain their extension while traveling.