The obvious defining feature here is sweet - the Thai version is sweeter than the usual Chinese/HK version. This is also a Thai-Chinese dish, so it’s not spicy like native Thai dishes.
The soup was savoury - like a very light broth/consommé - lighter than HK-Cantonese ones as they’d dropped Chinese ingredients for the soup like dried shrimp roe (ha chi), dried scallops and/or dried flounder when boiling the stock.
I must say that I “appreciate” the char siu for its uniquely Thai characteristics, rather than actually liking it. It can be regarded as a separate dish altogether from the Cantonese char siu prepared elsewhere in the Asia-Pacific region, where the original charred, caramelised effect comes though. I’d order it again. I’ll also try not to compare it with char siu as we know it 
