Yeah feasting on former light-fly sized fighters like Yong-Kang Kim instead of fighting the best in his own division is definitely something Khaosai can relate to.
Khaosai is not as monstrous as many make him out to be. The much smaller Kongtonaree Payakaroon outmoved him for periods, and sat Khaosai on his arse. But Chang is smaller than that, not powerful enough to stave Khaosai off at mid-range, nor strong enough (here at least) to work his crafty and tiring inside game. Khaosai hurts and finishes him at some point.
Would be very interesting to see Poontarat try and establish mid-range against Khaosai. Galaxy could put him down, but Payao could really get a rhythm and could burst into a straight-punching salvo and then ease off again. Would be very interesting to try and see Khaosai break him down with the talented Thai Olympic medallist sticking his jab in his face.