Hey as per my The Military Provost Staff are the Army's specialists in
custody and detention, providing advice inspection and surety within
custodial establishments.

MPSC Army

The MPS form part of the Adjutant General's Corps and are based at the
Military Corrective Training Centre (MCTC) in Colchester, Essex.

The Military Prison Staff Corps was formed in 1901 under Army Order 241. It
was redesigned the Military Provost Staff Corps in 1906

Eligibility criteria

As per my idea yes ex-serviceman of army can appear for MPSC

Qualification required

Candidate should be graduate

Final year candidate can also apply

Age limit :-

For general category : 21 to 30 years.

For the OBC candidates : 21 to 33 years

For the SC\ST candidates :21 to 35 years

Selection Process for MPSC Exam :-

Preliminary Examination

Main Exam

Interview