Do I need to maintain funds in my UK bank account to apply for a one-year Thai visa?

AND rather than let this turning into a "visa fishing" expedition 😮 I think the O/P has their options pretty well mapped out.

I think we took this as far as we could 🙂

Good luck to the O/P (y)

Your options might be get a Special Tourist Visa <- which will give you 9 months of stay inside the country (you get stamped in for 90 days and you can get two 90 day extensions)

It has some serious requirements to get that visa and it cannot be changed to any other visa type inside the country, so after 9 months you'd have to leave and get another visa

OR

Get a 6 month Multi-Entry Tourist Visa <- which is good for unlimited entries during the 6 months it's valid for with each entry giving you 60 days, and which you can extend for 30 more days for 1900baht. When that 90 days runs out, you'd exit re-enter the country and get a new 60 day stamp. You do that for the 6 months the visa is valid for and you can stay almost 9 months.

you are confusing a couple things that are completely different.

ONE is getting the year-long multi-entry visa from a thai consulate in your country (which does NOT require you to bank any money in thailand)

Keep in mind that year-long multi-entry visa doesn't let you enter and stay a year 😮 Every entry on that visa is limited to 90 days, then you exit/re-enter the country to get another 90 day stamp (given the requirements to get in to other nearby countries and back into thailand it is not the easy visa choice it used to be)

The 400K baht in a thai bank account in your name only is used to get the 90 day single entry Non-O visa INSIDE the country at the immigration office, and then get the year extension inside the country too. There's no requirement that you bank any money here if you're buying the visa before you come here.

As far as what the requirements are for you to buy the year multi visa from the thai conuslate in the UK go to the thai consulate in london's website and look at the requirements for the Non-O based on marriage to a thai.

OR

GO to the eVisa website, and start the application process, it will list the requirements.