SSI will allow shareholders who own two shares to buy one more at the price of VND15,000 a pop.
It plans to issue 497.4 million new shares.
The SSI ticker is being traded on the Ho Chi Minh Stock Exchange (HoSE) at around VND48,450.
The company issued 218.3 million new shares in September to increase its capital to nearly VND9.85 trillion.
The issuance, if successful, would see SSI continue as the biggest brokerage in Vietnam in terms of charter capital.