Indonesia Sex ratio
http://www.indexmundi.com/indonesia/sex_ratio.html
Cambodia - Population - Sex ratio of the total population
http://knoema.com/atlas/Cambodia/topics/Demographics/Population/Sex-ratio
Philippines Sex ratio
http://www.indexmundi.com/philippines/sex_ratio.html
Of the 3 links you provided regarding sex ratios of Indonesia, Cambodia and the Phillipines, only Cambodia indicates a minor surplus of females in the critical 15-24 year age bracket. So there simply aren’t enough females to meet Chinese demand.
Check Qatar, Kuwat, UAE Oman, Bahrain and Saudi Arabia’s sex ratios compared to China. Shockingly they have an even more extreme imbalance that manifests at the critical 15-24 bracket and gets worse with age which indicates that they have a serious problem with violence against women.