It's Time for Thai is great. On campus I don't really know that much since I live at UNSW Village and eat mostly in my apartment
But for coffee the coffee cart next to the library lawn is hands down the best coffee on campus, and their stamp card system is the best one (ten stamps and you can get whatever coffee you want for free, at Coffee on campus I think it's limited to a small cappuccino). JG's cafe next to the Chemistry Building/across from Red Centre has the best chocolate croissants (caramel glaze, really filling). White House has the cheapest coffee ($2.80 for a small, $3.30 for a large), but quality is inconsistent depending on the barista you get (generally it's quite nice, then on occasion it's the worst i've ever tasted). Their pizzas are great and around $10.