Chambeando is a colloquial and somewhat informal term for "working hard" or "toiling". It comes from the verb chambear, which means "to work".
In the context of this song, the singer uses it to defend his lifestyle, stating, "Pero lo que no critican es que me mato chambeando" (But what they don't criticize is that I kill myself working hard). It's an interesting word choice that highlights the gritty reality of his labor, contrasting with the criticisms he receives about his spending and social life.
Ever feel like everyone's got an opinion about how you live your life? That's exactly what Calibre 50 and El Komander are singing about in "Qué Tiene De Malo"! This song is a defiant anthem for anyone who's tired of the judgment. The singers are basically saying, "Why does it bother you so much that I like corridos?"
They're questioning why people care so much about their clothes, how they talk, what their friends do, and even if they're seen "ensillado" [on horseback]. They're quick to shut down rumors, stating, "Puro pancho eso es mentira yo soy hombre de trabajo" [That's all nonsense, that's a lie, I'm a working man]. They spend their money how they want, enjoy a drink and some music, and if they're seen with two women, what's the big deal? The song points out the hypocrisy: people criticize their lifestyle but don't acknowledge how hard they work. They love the good life, and they ask, "Y eso que tiene de malo?" [And what's wrong with that?]. They even say, "Qué escuchar corridos compa le aseguro no me hace un mal mexicano" [Listening to corridos, buddy, I assure you doesn't make me a bad Mexican]. It's a fun, bold song about living your life on your own terms and not caring what others think.