Is there a benefit of waiting till the last few days to get a 30 day extension?  is the extension from the day you apply for it or from the original end of the 45 days I’ve been here for almost 30 days now wondering do I wait till the end or just get it over with now?
TLDR : Answer Summary
It is advisable to apply for the 30-day extension early, as there is no downside to doing so. Most immigration offices in Thailand allow applications up to 30 days prior to the expiration of your current stay, and the extension will be added to your existing allowed-stay stamp.