The best translation is probably something along the lines of "I couldn't care less". Slightly rude, slightly humorous, definitely informal!

It means you don't care about something. It's a very informal way of saying. Literally it means: "Tô" = abbreviation of "estou", which means "I am" "nem" = "even" with a negative sense, more like "not even" "aí" = there (where the person you're talking to is)

hey! "tô nem ai" means "i don't care"

It means "I don't care" or "I'm not paying attention to it".

sinônimo não estou interessado não me importo não me interessa