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