Can I apply for a new Non-O retirement visa from the UK after my current visa expires?

Sounds like a reasonable plan!

1.) Get another Non–O E–Visa (Retirement over 50 years) from the Thai Embassy in London

2.) Do you already have the 800,000.- Thai Baht already in your Thai Bank Account??

if not, then have 800k Baht in your Thai Bank Account, so that on your next Entry months from now into Thailand on that new Non–O E–Visa you got from London, you can go to your local Thai Immigration Office to apply for an Extension of Stay with the 800k already 'seasoned' over 2 months while while you are away, outside of Thailand

3.) wanted to ask other Group Members: what are the Pro's + Con's of going from a Non–O E–Visa to Retirement Extension of Stay vs.

making Entry on free Visa Exempt, converting to Non–O in-country, then to Retirement Extension ???

Seems like there are many conflicting and confusing opinions here.. he tells us he has a 90-day non-o already which expires 2 Sep 25.. and he's intending to exit the country just before said expiry date.. and whilst at first it would appear to be sensible to apply for the 12-month extension of stay before leaving Thailand.. then bolt on a re-entry permit so it is valid when he returns in 4-6 month's time.. this strategy wont work unfortunately.. because there is the small matter of the 'under consideration' period.. if the 12-month extension is granted it will run from 2 Sep 25 when the current 'visa' expires.. they will stamp the passport 'under consideration' and he will then need to return 1-month later to get it inked into his passport proper.. that date will be 2 October 25.. which is after he has flown back to the Uk.. so that plan is not feasible for him.. the only option will be to apply for another non-o visa when he's back in the UK and begin the process to get the 12-month extension when he returns to Thailand.. which should not be a problem.

I would check with the embassy

Easier I'd say for you to get the 12 month extension plus re-entry permit rather than apply for a New Non-O. One thing to consider is when do you prefer your 12 months extension to occur, the same month each year that your current Non-O expires or the month that your new Non-O will expire when you return?

Get a re entry permit so you dont ne to reapply, non o will continue when you return

Should be fine. While there's no official limit to how many non-O visas you can get, the embassies would probably start to question it after a few. But a second one shouldn't be any issue at all.