What is Ah Ba?
When you greet somebody, say "Ah Ba!", raising the tone of "Ba" to express that you're glad to see the person.
Ah BA! is generally shouted out loud, because basically you don't give a shit about who's around you because the chances are they haven't a clue what you're on about, but the person you're saying it to already knows what it means..
"Ah Ba" can be said in any tone, generally to show how you're feeling, which is followed up with "What's wrong with you Ba?" or "Story Ba?"
To explain to somebody how hungover you are, just say "ah.. ba..." in a really tired tone, just to show how fucked you are.