Apply for a 60 tourist visa, used to be £25 then when here apply for a 30 day extension. Then go and apply for Non O visa whilst here when your 800k has achieved the required period in the bank.
on WISE, reason for transfer "long term stay in Thailand", I may have got the terminology slight wrong. It should then show as "International Funds Transfer". I say should as its not 100% certain at times. If the transfer shows as "Interbank Transfer" I send the money back via DEEMONEY and transfer back via WISE again, checking that it shows as "International Funds Transfer".