I would say while you're back in the UK, you could apply for a year-long, multi-entry Non-Immigrant Type O-A visa based on being over 50 from the thai consulate in London.
To get that visa you do not need to bank any money here in thailand (you use your account in the UK to show proof of funds). The visa is good for a year from the date it's issued, is unlimited entry to the country with each entry getting you stamped in for a whole new year for the validity of the visa.
Hands down it is the best visa to have BUT you get it in your country BEFORE you come here. It can't be gotten here..
This tells you about the visa
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