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