I have done this, you must cancel your work permit and get a leaving document from your company, which you can take to immigration the same day as you make your retirement vida ext. So dont forget your 800kthb needs to be in the bank for 2 or 3 months, not sure 🤔
The enforcement by thai immigration is denying visa exempt more than 2 times if its back to back, on the 2nd one you can only extend it by 7 days. Enough time to get out the coutry. You can come many times if you travel back to your country and have some space between trips. You must look like a tourist with hotel booking, flight out etc