Or do it online, if online does not work (you can't go past the first page) then you can also send it by mail. Just the paper/copies, not the actual passport.
I had them check it last year when I did my last Thai Wife extension, after the 4 weeks "under consideration" I had to show the bank book again, in Chaeng Wattana. Since this year I changed to retirement, way easier than all the hoops you have to jump through with Thai Wife.
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