For retirement you need 800k for 2 months before applying for your 12 month extension and maintain that for 3 months into the extension. The minimum then cannot drop below 400k for the rest of the year of your extension.
It is regarded by Immigration as a type of Tourist Visa so you need to meet the requirements for a tourism entry stamp. Risk it at your peril but don't advise others.
There is nothing in those lists which have Visa on Arrival in the title (which, if you knew anything, VoA is a Visa which costs 2000B on arrival for certain passport holders to get a 15 day entry stamp which cannot get extended).