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