HSBC runs an archive in Hong Kong. As you'd expect, most of their materials relate to the bank's business, but there are other ways they can help, including:
People. If you have an ancestor who worked at HSBC, it's usually possible to reconstruct their career, including when and where they were posted around Asia. You may also find mentions of them in the bank's minutes of various meetings. (If you're researching an ancestor who worked at the HSBC, you should also visit the "Silver Bowl" website, which has lots of information about that topic.)
Photos & paintings. General illustrations of Hong Kong. Mostly from late 1800s til 1930s, but also some staff albums with photos from the 1940s and 50s.
General history. The archive holds several editions of "The Chronicle & Directory for China, Japan, & The Philippines", which has lots of useful information about people and businesses in Hong Kong. (You can see an example of the 1872 edition at http://gwulo.com/node/9267).
There are also oral history recordings taken in the 1970s & 80s, that include descriptions of life in Hong kong in the preceding decades.
Here is HSBC's own description:
Bank history and archives
The Bank's Archive department preserves and provides access to HSBC's archive collections in the Asia-Pacific region. HSBC's historical records and art collections can be used to answer enquires from the community and to support research and exhibitions.
Researchers wishing to make an appointment to visit the Archives can contact us at the following address:
HSBC Asia-Pacific Archives
The Hongkong and Shanghai Banking Corporation Limited
1/F Tower 2 & 3, HSBC Centre, 1 Sham Mong Road
Read more on the HSBC website.