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