Armin's answer is correct. However as for your concenrn about which one is actually more correct, I have the following opinion:
1- I am hired as a manager is technically correct, but it pictures as if you are delivering a news to someone. As if you have just been hired and youwanna tell someone about it. So again, I have been hired makes more sense.
So I you wanna know where I am hired would make more sense, here is an example:
a: Hey Nikoo, we hired you.
Nikko: Wow! so you mean I am hired as a manager?
2- I am occupied as a manager does not make sense here! It pictures as if you are telling someone "Hey I am busy, don't you see I am occupied as a manager!
3-In my opinion, I am employed as a manager is the best choice to go for. I am employed can be used by someone who has just been employed (day 0) to the end of his career. So any time you ask him about his job, he can say "I am employed as ..."
Hope it helps.
So "I am employed ..." is the best choice.