The K and the NG are the only 2 somewhat tricky sounds of Bahasa Indonesia. The former has a dual function. Sometimes it sounds exactly like the K in English, while at other times (like in Pak) it marks a ‘glottal stop:’ a glottal stop is the opposite of the ahhhh-sound, as you intentionally choke off the air in your throat to end the syllable. It sounds like the Uh in Uh-oh! The second is the NG combination which produces a “velar nasal” sound similar to the way you would pronounce ‘sing. ’ All that said, it is a minor matter that the Locals will tolerate until you eventually refine it as you learn more of the language.