Short answer: yes, it is possible. If you use e-services across multiple countries or, for example, have bank accounts in different Baltic countries, it is possible to use the same Smart-ID account to access them.
However, how and if you can actually log in with the same Smart-ID account depends on the service provider and if they allow access through foreign national ID-numbers. Please contact the service providers (i.e. banks) for further details and instructions.