The first stage is a CV screening, if your CV is impressive and you made it through, the next stage is a phone interview. Pretty basic phone interview, they'd ask questions like, "what do you know about PMI?", "why are you interested to join us?". Here you cold also ask questions if you're not sure about anything.
The third stage is a half-day semi-orientation/interview session. It's basically a morning where you attend simple talks by previous management trainee and they explain to you what the career is like and what is expected. Then you would proceed with a 1-on-1 interview, a pretty casual one. The whole purpose is to get to know you better. They'd ask questions like, "what do you think of the company?", "what is your stand on smoking?", etc.
If you make it through this stage, there would be an online assessment. It's divided into three sections, the first is a numerical assessment, basically it's some simple calculations and math questions. The next section is logical reasoning, some sort of an IQ quiz, it can be a little bit tricky, most of it is predicting the next pattern in an assortment. And the last section is reading assessment. There will be a paragraph and questions following it. It is leaning more towards English assessment where there will be questions like, "what is the meaning of this word in the paragraph?".
Making through this round would mean the final stage, which is a case study presentation. Basically it is a simple scenario and you are presented with three solutions to the scenario. You will need to pick one and then present it to a panel with justifications. The scenario presented are not related to PMI and the businesses they do, it's more of an open topic. During the case base session, they will also ask you regular interview questions. As this is the last stage, you will know if you managed to make it through or not after this stage.