Better to come over on a 30 day visa exemption during that time try to open a bank account and apply for an O visa here transfer money into your Thai bank from the UK I suggest one of the 3 banks that don't have limit restrictions wait for your money to be in your bank accounts for 60 days then apply or get an agent here to do your extension
Or try looking at you on retirement visa and her piggybacking on yours not sure if that changes the money situation but have heard others speak about it