It is possible to pursue a Polytechnic education in Singapore with an N-level qualification. The N-level qualification is typically obtained after completing the Secondary 4 Normal (Academic) or Normal (Technical) curriculum.
After obtaining your N-level results, you can apply for admission to a Polytechnic through the Joint Admissions Exercise (JAE) or the Joint Polytechnic Special Admissions Exercise (JPSAE) depending on your qualification and circumstances. The admission process might also involve taking into account your N-level results and the courses you are interested in pursuing.