If you've got the 800,000 baht in a financial institution account, you should update your bank book on the day you visit the immigration office, as you have to demonstrate that the money is still in the account. You're only permitted to leave with more foreign currency when you have approval of a bank. There isn't any limit on the quantity of currency that it is possible to bring into Australia, but you're going to want to declare amounts over $10,000.
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