There are actually several ways to say "hello" in Syan, kiaa is a very neutral and formal option. Other options are:
Bia-kiaa = neutral and if you haven't seen the person in a long time
Ki-moa = friendly and excited/happy
Garis-a moa = if you've never met the person before
Moa omin-a aad = happy/welcoming but still very formal
Kikiaa = a more cheerful version of kiaa
Kiaa di-o'moa = very formal (to a group)
Kiaa di-o'akaado = to show respect (to a group)