Well now we're just arguing semantics, but here's Dictionary.com's definition of fraud: "deceit, trickery, sharp practice, or breach of confidence, perpetrated for profit or to gain some unfair or dishonest advantage."
I don't know if getting a second job wouldn't be fraud in a strict legalistic sense, but it definitely meets the above definition.
Anyway, if you wanna do it, go ahead. I'm not going to risk it myself, but I've worked at plenty of companies which were badly-enough run that I can imagine getting away with this kind of behaviour. I've also worked for employers who treated me like garbage, so I can understand why some people might have no objection to treating their employer like garbage.