It’s about wording. There is no such thing as a “retirement visa”. When you want to stay in Thailand longer than 3 months, you start with a non-immi O visa. The visa is valid for three months. Before expiry you can apply for an extension based on either retirement or marriage to a Thai national (I believe there are more forms, but these two are most common).
You agent says ‘retirement visa’ but should have said ‘extension based on retirement’.
The non-O visa is basically a foundation on which you get the extensions. Once you have a one year extension (which must be repeated every year) you will need to subject to 90 day reporting so immigration knows where you are. (Easy process which can be done online).
As a British citizen you can enter Thailand for 14 days without visa.
Bermuda is not a country but a “British Overseas Territory”. Visa exemption is (a.o.) for holders of passports of Great Britain and its overseas territories.
I am confused. I was told just a few weeks ago that you can apply for a 90 day non-O visa within Thailand, but now you seem to write that after entering on a tourist visa one must leave Thailand and apply at an embassy outside of Thailand...
What is the real procedure and where can I find positive confirmation on official sites?