It is possible to go for an MS degree after BAMS like MBBS in India . But there will be an obvious difference between the two. MS after BAMS will allow you to do surgery through Ayurvedic techniques which is very different from MBBS doctors. Thus MD is more preferable after BAMS.
I hope it cleared your doubt.
There is no way that MS after MBBS and BAMS is same. They are entirely different courses where students learn their own courses in the particular area of interest.
While BAMS is Bachelor in Ayurvedic Medicine and Surgery, MBBS is Bachelor in Medicine and Bachelor in Surgery.
MS is pursued to become Master in Surgery. In BAMS you do learn surgery methods but you do not have a legal medical license to perform a surgery as a professional. The only surgery related action a BAMS learner professional can perform is only on Minor Cuts. There is no way that you can perform legal complex surgery operations which are operated by real doctors. Both are different in terms of pathy and work process. There is huge difference between the two about which it is better to be learnt about by Professionals.
I would suggest you to go for MBBS and then MS rather than BAMS after then MS. Choose the branch which suits you more.
MS after MBBS is learning surgery and related specializations as per Allopathic practices and options available.
MS Allopathy is Master of Surgery and they do real Surgery .
MS after BAMS are properly the methods of surgery as per Ayurvedic principles.
You cannot perform any kind of surgery legally . Maybe some minor cuts without using local anaesthesia.