first round: face-to-face with HR, can be very short (10 to 20 min). Not very technical. Just be confident.
second round: one-day Assessment Center, which includes group discussion, individual biz case analysis & presentation, numerical & verbal test.
third round: final interview with the heads of the division you are applying to.
Comments: surprisingly, OCBC's graduate recruitment process is not as easy as, or in certain way, tougher than some global banks, i.e. HSBC Private Bank, Stanchart, Lehman, JPM, to name a few (all from my personal experience). So do prepare well if you are serious about this position.