Very easy, go to Flightradar, choose Smartlynx Airlines there you can see all registered aircrafts flying for Smartlynx then check the flight numbers which you can easily identify which airlines they are working for out of which bases. Vietnam was 3 years ago last time. This year several UK, German, Belgium and Moroccon bases. Also Ireland, Portugal and Egypt. Not to mention their home bases Riga and Talinn.
Often you don't have luxury to choose your base. Company assign you %80 of the time where ever they need you. End of the story. Expect long waiting for starting line training since company is overwhelmed by too many new pilots, limited training capacity.