over time
you are paid very generously per hour of flying. Also known as, flight pay. So if you are rostered, say 10 hours of actual flying, excluding sign-on, pre-flight briefing, you are paid flight pay for these 10 hours, and that's it (above your full-time salary of course). Beyond that, forget it.
So if your flight hours are rostered as 90 per month, and you actually 'fly' 110, - great! Put the extra 20 down to good faith.
Could be worse, you could be unemployed or working in a boring role.
Tiger does offer the opportunity to fly. You just need not be be a princess thinking you're working for Thai or Cathay - ain't gonna happen.
All the best!