With a CRL rank of 381,094 and OBC-NCL rank of 136,581, admission to IIT Patna’s BS-MS program is very unlikely because the cutoffs are much lower. This program is highly competitive. You can consider other state or private engineering colleges where your rank fits better. Improving your rank by preparing for JEE Main again is a good idea. Also, IIT Patna’s BS-MS program requires good board marks and clearing entrance tests like IITP-SAT. Let me know if you want help finding other options!