This word is mostly used with epithets referring to famous and important people as an honorific, kind of like "Mr." e.g. Sang Raja = The King. It is also used as an epithet for the Indonesian flag to anthropomorphise it: Sang Merah Putih ("Mr Red and White). It can be used to personify animals in stories and sarcastically to refer to people who think they are more important than they are. So it's not a one-to-one translation of "the".
I beg to differ.
It's just "THE" or "that" but in a poetic way of saying, just like you said: "sang raja" but NOT an honorific, it's just "the king", a known king or a king that has been mentioned before in a story.
Sang Saka Merah Putih = The Red White Heritage
sang kancil = the mousedeer, sang harimau = the tiger