Hello student,

It is not possible to give 12th exam twice from the same board when you have already got passing marks. Only the students who fail, are allowed to re appear for 12th exams.

In order to repeat 12th, you have to opt for some other state board, do your 12th with mathematics and physics and then apply for NDA to get admission in merchant Navy. But remember the age limit for NDA to apply is 16.5 to 19.5. I hope you don't exceed the limit till then.

I hope this information helps you.

Here is all you need to know about NDA.

https://www.google.com/amp/s/competition.careers360.com/articles/nda-eligibility-criteria/amp