@Will *****
Yes, you need to leave before your existing stay permit expires
*** then re-enter Thailand visa-exempt and get stamped in for 60 days
*** fill up your bank account above the 400.000.- THB mark. No seasoning required at this point!
*** visit Immigration with your updated bankbook showing the 400.000.- THB sitting in it, a rental contract (or your wife and her housebook & ID card) and apply for the
“Change of Visa Type”
From the 60-days visa-exempt, to the 90-days Non-Imm-O family visa.
***you will be required to pay 2000.- THB for this application to the “change”
*** the 90-days Non-Imm-O visa will be issued “under consideration” for 14 days (hence for the application to the change, a minimum of 15 days must be left on your stay permit stamp!)
*** You pick up your 90-days Non-Imm-o visa on the date they gave you
***As soon as the 400.000.- THB have been sitting in your account for two months, and you got the “bank letter of guarantee” to show this
you can apply for the “1-year Extension of stay based on being married to a Thai wife” using the 400K deposit as financial proof. This application will cost you 1900.- THB
*** And you will be back to where you lost the thread. Never ever let the deposit fall under the required amount
*** in case Immigration tells you that you need to prove a 2-months seasoning of the 400.000.- THB for the application to the initial 90-days visa, then just buy yourself the time by either extend the visa exempt entry by 30 more days, OR by applying for the 60-days “family visit extension”