I know a couple, who joined Temaesk Polytech and a couple in Ngee Ann.
All of them took 4 to six weeks, from the time they got through the second interview, before they got the offer letter, and another 4 weeks or so, before they were given a starting date, starting date coinciding with the start of the semester. I had to baby sit them, so i know
The only exception was a friend who joined Ngee Ann, who did her homework - got her uni to send in the verification letter directly, once she was notified of the short listing
She did ask the HR before doing that ...