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