This 800,000 does it have to stay in the Thai bank for the entirety of the visa. Or can the bank account holder take it out at some point in time. Then deposit it back when the visa is due for its renewal.
Go into the Halifax. Sit down with them. Explain the situation. And surely they will transfer 800,000 Thai baht in one lump.. If they don’t, change banks. i think some uk banks are giving an incentive of around £175 if one does their business with them….