According to the official website of the National University of Singapore, students can't postpone their enrollment in the first semester, and must report to the school and start classes within the specified time. Therefore, if you are admitted to the National University of Singapore, you need to go to the campus and start classes at the time stipulated by the school.

Under some special circumstances, such as sick leave or unconventional circumstances, students can apply to the school for suspension or withdrawal, and re-apply for admission next semester or school year. However, these cases must be specially approved by the school and relevant supporting documents need to be provided.

If you can't get to school within the specified time, I suggest you contact the relevant departments of the school in time, explain the situation to the school and apply for an extension of admission. If you need to postpone admission, the school may ask you to provide relevant supporting documents and make a decision according to the specific situation.