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