Wing Boy
First of all, do you have a Hong Kong ID card? If not then you need to have a CPL just to be considered for the cadet program. I really suggest you research more into this as it doesn't seem you have done much. First of all, the training in the Cathay Cadet Program is paid for completely by Cathay, you are only bonded for 6 years of service. In the cadet program you will be assessed on your flying skills based on how many hours you have, that way they are not assessing someone with zero hours against a PPL holder. Getting a PPL won't hurt (apart from making flight grading harder) and it would show enthusiasm but in my opinion it won't help you that much.