study in Korea international student job rules korea student visa transfer Korea student visa instability Korea student attendance Korea part-time work Korea university change immigration Korea student visa attendance rules Korea student visa after graduation international student administrative risk Korea student work permit Korea international student attendance Korea student visa Korea D-2 visa Korea hikorea d10 d-10 visa korea international student immigration review Korea student visa korea rules international student korea immigration attendance korea international student visa korea problems part-time work Korea international students D-4 work permission student visa korea attendance rules student visa document mistake Korea student visa korea attendance work rules international student korea immigration Korean university visa student visa pattern issues Korea student part time work korea visa international student Korea D-2 part-time job international student visa rejection Korea job seeking visa korea