National University of Singapore

See on the website its specified that a person will be eligible for admission only if the candidate secures at least 90% marks in all his board subjects (of course excluding Hindi in your case), so maybe your physics marks mess up your chances of getting admitted in that particular college.
Best of luck.

Steps: The common steps to applying for admission are:Search for colleges and courses. Contact schools and visit websites for information. Narrow down your list of schools. Take the entrance exams like GMAT GRE TOEFL, IELTS. Write Shops and ask for LORs. Apply to colleges which fit your interests.

Your class 12th score is low, as they generally require at least 60 percent in the boards and you have a lot less so not sure about passing the criteria.

If you get good score in SAT with good score in subject test and good extracurricular activity, you may surely get a call from the University of your Choice.