This can happen if you talk casually, either in text messages or in face to face conversation.

nggak = tidak (no) --- variation: gak, ga, ndak

entah = tidak tahu (no idea/do not know) --- variation: ntah

gapapa = tidak apa-apa (it’s ok) --- variation: gpp

wkwkwk = hahaha (laughing sound) --- variation: hihihi, xixixi, awokawokawok

Expect also many repetitions of the word ‘ha’ (‘huh’ in English, pronounced like ‘huh’ too) which can means many things, from disbelief to excitement, from asking you to repeat your words to expressing disgust, from feeling surprise to questioning your judgement. So if you hear this word someday, just use your imagination ;)