Casual workers exploited

CAN somebody from the Labour Department explain to us casual workers of this nation the laws that govern our work?
I don’t know if my employer follows the rules when it comes to my employment entitlements.
There are 15 of us and we don’t have Nasfund contributions.
What if you have been a casual for five years and don’t contribute to Nasfund until the fifth year, what happens to the missed past four years? We have no annual leave entitlement and no overtime pay.
If we work overtime we get paid normal rates, nothing extra.
We don’t have sick leave.
Casuals, even if you are on your sick bed, you still have to go to work, so tell your doctor to give you some strong medicine.
There is no bereavement leave. You will not be paid even if you bring in the death certificate of your own son.
We don’t get a bonus, like at Christmas, for example.
Can a casual worker be a casual worker for the rest of his or her life, with his or her pay unchanged?
Surely there is a law that protects casual workers from exploitation and we want the government to clarify and enforce those laws.
If companies or organisations breach those laws, what penalties do they face?

Mr PNG Casual