“Bây không nói tao cũng không biết!” (I wouldn’t have known if you hadn’t told me.)
“Bây” (or “bay” in Northern lingo) is a familiar pronoun used by Southerners, especially those in the Mekong Delta. “Bây” (or “mày”) refers to 2nd person in conversations, used normally by older people to call younger ones or among peers.