The 30 day extension starts the day you current visa expires. You don't have to wait until the last moment either. You can go to an immigration literally on your 2nd or 3rd day of entry and get the 30days.
The main thing you are missing is a Thai bank account with 800,000thb in it. This money needs to be in there for two months before you can apply for your retirement visa.
not needed for 30day extension on tourist visa. TM30 only for those on long stay visas (retirement, DTV etc) when you have to report to immigration every 90days with proof of residency which is what a TM30 is.
We done cooking classes.....you need to go Thailand first, enroll in classes, get classes sign up letter confirmation, DBD documents that prove Muay Thai school is legit. You then need copy of Thai owners ID Card signed. Also need Thai bank account with 500,000thb in it. Then you go to Vietnam/Laos etc and apply online. You cannot apply for DTV in Thailand. Bloody long hard process. Stick to 60day tourist, visa extensions and border runs