Are you still looking at working for the kindergarten attached to the school, or for the IB school itself? IB is a high school program a bit like AP in the States.
If it is the IB high school it should be pretty legit. And like Amonk said, you'll need proper qualifications. If it is just the kindergarten it could be a completely different story. Lots of international schools (mine included!) have feeder kindergartens which are actually pretty autonomous. The kindergarten probably wouldn't require credentials like a proper teaching certificate, whereas the actual IB grade school would. It still should be better than your run of the mill Chinese kindergarten, and should pay accordingly, but maybe not quite Western standard (I'm guessing though, at least 10k a month?). Like Amonk says, if you were working for an actual IB High School, you'd expect pretty much a Western teacher's salary, hours, etc.
I'm thinking this is the kindergarten though, right?