Just been to Krung Thai bank and they said the letter we have is acceptable, but they need a Thai driving license as a requirement as well, so pressure is on to pass on Thursday!
It costs nothing is my understanding, you just get another 60 day visa on arrival or visa exempt. I'm aware they are clamping down on border runs but I think as I'm married with driving licence letter of residence etc they'll look on me favourably, accepted it's not guaranteed in which case then I'll pay the fee. That's my thoughts anyway
my wife just spoke to immigration and you're right, another 500 baht ☹️. But like all Thai's they are super helpful, they said don't just come and get it, go to the banks first and find out if they accept it. They also said to just go over a border into Vientiane or Phnom Penn and apply for Non-O at the Thai embassy there, we were thinking we'd have to go back to the UK. Thanks Lyndon.