Indonesians have a very rich conception of status, age and familiarity being the two main components that constitute their forms of address. A lot of the forms relate to family member names. What I like about this is how it seems to make everyone an insider. Indonesians don't judge on the basis of gender or race or class, but they very much do on the basis of relative location.
Bapak: literally "father" now is used to refer to any older man (like 'sir'). Often shortened to pak. The Indonesians love to shorten things.
Ibu: literally "mother" refers to any older woman (Madam, miss, Mrs.). Shortened to Bu.
kamu: "you" among intimate equals