yeah, ketjap manis is indonesian. my current and previous helpers all use it. it's basically the #1 seasoning in indonesia. they don't use chinese soy sauce, but use ketjap manis instead.
in singapore/malaysia, they have hainese chicken dark sauce, which is even thicker. (bottle on the left)
the chinese grocery will also have a version of thick soy sauce, but it's just regular soy sauce with starch thickner. we don't have this because it's usually gross..
edit: i just skimmed through the pitmaster x ketjap video. indonesia has a big influence in the netherlands.. lots of indo culture there.