How long do I need to keep 400,000 Baht in a Thai bank account to apply for a 1-year visa extension after entering on a 90-day Non-O visa?

the 400K baht has to be in a thai bank account in your name only for 2 months before you can apply for the year extension on the 90 day non-O you will enter on

SO once you get here, get the funds in the account as fast as you can. After it's in there 2 months you can apply for the year extension at your immigration office for 1900baht

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During the time it's 'seasoning' you and your thai wife should go to the immigration office and get the hand out listing all the required documents needed so when it comes time to go do the extension you can pull it off without any problems