Despite common belief no they are not the same thing. Just like there are numerous different types lawyers e.g. criminal lawyer, family lawyer, property lawyer, there are also lots of different types of accountants too.
The title accountant is a broad term for anyone who has a qualification in accounting. In the accounting profession there are management accountants, tax accountants, financial accountants, cost accountants and the list goes on.
A tax agent is an accountant who is registered by the Tax Practitioners Board and like the BAS agent they must have minimum qualifications and experience as well as have specific insurances in place and also maintain their knowledge by mandatory continuous professional education.