Hi there,
12455 rank in SRMJEE can be considered as decent.
You have a good chance of getting any branch you would like to choose. Here is the list of branches you can get with their respective campuses.
1) SRM Chennai ( All except CSE which closed at around 10,000 so you have a little luck with it too)
2) SRM Ramapuram ( All branches)
3) SRM Vadapalani ( All branches)
4) SRM Ghaziabad ( All branches)
5) SRM Sonipat ( All branches)

So, except CSE at the Chennai campus, you have all branches open to you.
Hope it would help.
Thank you.