In reply, the hosts also made a confident start to be 66 for no loss .
Apart from Prem's 101, which was laced with seven fours and two sixes, Sachin Baby also did well to be second highest scorer with a 51-run effort.
At stumps, Anshul Gupta (33) and skipper Soumik Chatterjee (28) were holding fort for the Services.
Brief Scores:
Kerala: 322 all out in 151 overs (Rohan Prem 101, Sachin Baby 51, Diwesh Pathania 2/84).