@Al**
people say this but I honestly don't think it makes a difference. Meeting whatever the specific documentation requirements the branch wants, exactly, is more important. If you meet the requirements you can open an account with 500B.
Sometimes being willing to buy a cheap insurance (like a few hundred baht) maybe can help, but I don't think anyone is impressed by your slapping down 800,000.
800,000 isn't large enough to cause problems but if anything slapping down very large amounts of cash (above US$50,000) will only cause more compliance documentation for the bank and is more likely if anything to be a negative IMO.