How long does the 500,000 THB need to be in the bank for a DTV Visa application in Thailand?

Do you need to prove you still have the 500k when you enter the country? I’m worried that for a short period of time my bank will show less than is required after I get my visa?

Why not get a marriage visa?

why dtv? you can apply non o visa as spouse of thai citizen

In my opinion after applying in Ho Chi Minh the 500K need to be in Your bank account at the time of application. Even they ask additionally to submit 6 months bank statement it was irrelevant that I had my 500k only for few days. The reason why they want to see 6 months transactions is not known. In my opinion is not relevant that You married or have children in Thai to apply for DTV rather than there should be another visa in Your circumstances but defo not so great as DTV.

I am over-simplifying the particular requirements and details of the DTV Visa, but think about DTV Visa like it's a 5 Year Multiple Entry Tourist Visa where they are 2 main pathways to qualify for the DTV Visa:

1.) Remote Work, Digital Nomad, Workcation: Work done for things outside Thailand and income is mainly derived from outside Thailand, but you're doing such work virtually while physically inside Thailand;

2.) Thai "soft power"/medical tourism/long term medical visits: "Soft Power" can emcompass many things, but so far, have seen Muay Thai training courses, some have been able to have long-term Thai cooking/Thai cuisine courses, medical visits encompassing long-term care and several visits over a prolonged period time....

Having said all this, perhaps looking into a Thai marriage visa or Thai visit family visa might be a better option for you if you are not going into those 2 main pathways for the DTV Visa....

I showed a statement for 1 day with the funds and it was accepted. I applied at the London embassy

Your bank transactions make no difference. As far as how long the bt500,000 has to be in your account, that all depends on where outside of Thailand you apply, as you can not apply inside Thailand. The time period can be from a few days up to 6 months. It just depends on where you apply

From your description of yourself, you don't qualify for the DTV Visa.

What is your plan for making an application?