Hey

once you complete your MNS, you still have to appear for NEET and go through the process of studying to become a MBBS doctor. If you want to become a doctor in the military, there are 2 ways about it. You appear for NEET, qualify and secure a seat in AFMC, Pune. Once you complete the course, you will have to serve the Armed forces for a bond period and if you want further to stay there, you can continue to serve the Armed Froces in the capacity that you are offered. But let's say you secure a MBBS seat in a civilian college, you have to complete the course and then appear for SSC exams so as to enter the Military forces as a Doctor. There is no lateral entry for MNS to MBBS. It is from the scratch and through NEET.Sorry to say but you cannot become military doctor after NMS in army, for that you will have to clear neet exam and then after AFMC counselling you can become a doctor after complete study, for more detail about AFMC.

go with the below link.
https://medicine.careers360.com/articles/afms/amp

Good Luck.