移民美國弟弟香港開銀行戶口，有乜手續-無香港住址

Personally, I don't want to answer this one. But since you have asked twice...

The actual requirement is your brother needs proof of address. It does not mean the address has to be in Hong Kong.

In other word, as soon as he allows the bank to use the address in the U.S., he can still open the account.

(You can check with the bank and verify that.)

Also, your brother can also request international banking service to open an account in advance. Banks, such as Bank of East Asia, HSBC, Citibank, provide such service. However, it may not be a free service and there may be an asset requirement.

In my opinion, your brother should not open an account based on that $6000 (since he can cash it from Standard Chartered).