Tumbado literally means "fallen" or "laid down," but in the context of this song and the genre of corridos tumbados, it takes on a much cooler meaning.
It describes a style, an attitude, and a way of life that is relaxed, confident, and authentic. When Justin Morales sings, "Y ahora véanme bien loco y bien tumbado," he's inviting you to see him as someone who is wild, but also effortlessly cool and true to his unique style.
Justin Morales lays out his life story and philosophy in "Desde Morro." He starts from the beginning, explaining how he was raised: "Desde morro me enseñaron a ser bien cabrón" (Since I was a kid, they taught me to be a badass). He credits his mother for raising him with respect and his father for giving him some very direct advice. His dad taught him to be real and, most importantly, "pórtate mal con quien sea un culero" (act bad with anyone who's an asshole). Justin says this advice changed his life, leading to the person he is today.
He's now focused on making money—"Pacas verdes es en lo que yo siempre pienso" (Green stacks are what I always think about)—and believes the only way to get it is through hard work. The song also touches on loss and loyalty. He honors his late brother, Brandon, who he has tattooed on his neck, and gives a shoutout to his crew, his clica. He makes it clear that loyalty is everything, noting that he counts his real friends on his fingers. It's a song about coming up from nothing, staying true to your family, and proving the doubters wrong.