Why are other countries, like Yemen and Cambodia, coming to Indonesia to get their commandoes trained? In a word, reputation. The Indonesian special forces, called Kopassus, is regarded as the best in the Pacific area. Founded in the early 1950s, their training methods came direct from the World War II British commandoes, via a Dutch soldier who served in the British commandoes, and retired from the Dutch army while in Indonesia. The Indonesians took to the tough training, and maintained those standards. Kopassus has mainly been used against separatist, rebel and terrorist groups within Indonesia. While Kopassus acquired Western military skills, they still retained Indonesian attitudes, which meant that they were pretty vicious with "internal enemies." Lots of torture and mass killing. This gave Kopassus a bad reputation, but mostly from foreigners. Militarily, they are highly regarded, although American advisors have long tried to convince that a less violent approach to hostile civilians might work better.
Both Cambodia and Yemen share the bloody minded Indonesian attitude towards internal dissent. That might have had something to do with going to Kopassus for special operations training. Sort of a "they speak our language" thing?
Kopassus currently consists of a headquarters, two brigades of special forces (three battalions each), and an 800 man counter-terror unit. There is also a training center with 400-500 troops, and a company sized combat intelligence unit.