From what I read, in Thailand it typically include the following ingredients, few of which seem to be in any version I’ve had in recent years:
preserved radish or turnip (hua chai po)
shrimp paste in oil (gach tôm xao dau an or tôm nâu bún riêu)
shell-on dried shrimp (kung haeng)
Chinese garlic chives (gao choy)
I know that some of those are often served on the side so you adjust it to your own liking.