What you have in a U.K. Bank has no bearing on a Thai marriage visa application, you can travel to Thailand on a O visa based on marriage obtained from Thai embassy in London, which will last for 3 months, after 2 months in Thailand you can apply for a marriage visa , it is then that you need to show proof of funds .
How much cash are you allowed to take out of the UK?
New rules on declaring cash when entering or leaving the UK. HMRC has announced that from 15 June 2007, if you are travelling to or from a country outside the European Union (EU), you will need to declare any sums of cash of 10,000 Euro or more (or the equivalent in another currency) to HM Revenue & Customs (HMRC).
in my case, being a marriage visa only requires 400,000b so at today's rate is only £9,113, I will possible be using Transferwise, but as I will probably return to UK twice a year, cash is an option.... ps maximum cash allowed legally is $20,000 / £15,151
So following on from that, does it have to show the funds were transferred from a bank outside Thailand or could I return to U.K. And bring cash, exchange it at Superich & deposit it to my thai account for 'seasoning'.