OK so you are not renewing anything, you are applying for a new Extension of Stay based on retirement (by meeting the financial requirements) which can be done up to 30 days (or 45 days) before your current stamp expires. Do not wait until the last day as your original post suggests you will do.
Don't do your Visa (I assume you mean Extension of Stay) "renewal" on the last day, it can be done up to at least 30 days in advance (45 in some places).
This is why terminology is important to get the correct answer. It is not pedantic to correct people as others read the advice given to the original question asked.
The cost and speed depends upon the Immigration Office your TM30 is filed at. I got my residence certificate in Sa Kaeo province free in about 25 minutes (it took that long as the front office person I was dealing with had never seen an online TM30 before).