You need to give us more info.
was it petty theft?
was the theft of intellectual property, money or goods? was it more than one of them?
was it a one off?
did the crime take planning and thought?
was the crime committed over a period of time?
what is the nature of the employer? (eg. financial, retail etc).
and yes, if you received a conviction that would rule out travel to quite a few countries - definitely canada and the USA; possibly even some of the EU. The AU authorities will ask the nature of the crime, and if it is driving related they won't care, but I am unsure about the other offences. I certainly would not rule it out.