I closed my Hong Kong HSBC accounts several years ago from Canada after I left Hong Kong.
Via the messaging system in the online banking interface, I asked to close the account. They replied saying that I would have to send a written request via registered mail. The account had a residual balance of a few dollars and they suggested that I include instructions in my written request to have that balance donated to the Hong Kong Red Cross.
A week after the letter was delivered to HSBC, I could see online that the balance was donated to Red Cross. A few days after that, I no longer had online access to the account. Then a few weeks after, I received the final statement in the mail.