It is used in the south of Brazil, usually in Rio Grande do Sul. It means a lot of different things, but it’s normally used to refer to a person.
Mas báh, TCHE, tu viu que sol lindo que está fazendo hoje? Presta atenção no que eu estou falando, TCHE. TCHE! ( in this case, the expression is used only to give emphasis to what you are saying. It’s basically suitable for every situation)