Chuaj:
Your chances in getting into SIA really depends on your previous experience, like how long did you join for, what aircraft type(s) you flew, how many hours you logged and why and when you got terminated. I am one myself, and yet, I know of another who did not clear the 2nd interview.
As for your choice of study, it will certainly help if you are technically inclined, as having an engineering degree will help in understanding most of the aviation subjects, especially technical ones. Having said that, there are also many Economics / Finance graduates who do well in SIA, so, up to you to decide.
EchoPapa:
Right now, it is the company's stand that trainees are highly recommended to own their personal laptops. This is because most of the documents will be issued in CD-ROM format. And yes, there is internet access available, going for approximately A$1 per hour of use. This may change in the future, but for now, that's the rate. There are also phone available for you to call home, you just have to purchase your own calling card, and just dial from there. Downside is that there are only 2 phone shared among 100 trainees... so, gotta share.