Nobody in their right mind would be opposed to locking up child abusers, but there are rights and privacy issues that require concern. Are they merely assisting the Cambodians in applying their own laws? It does look like they are going beyond that. Which country's age of consent is applicable? This varies by state in the US, sometimes drastically. Will suspicions about child sex tourism be used as an excuse to search hard drives and memory media of returning US tourists? Do I have to be concerned about photos on my HD of my own kid frolicking nude on a beach in Thailand? From what I have heard, I do.
As I said, the stated motivations of the government are good, and if it gives sex predators pause, fine. Nonetheless, the possibilities for excess and abuse by law enforcement are serious. It might be more effective to encourage the Cambodians (and Thais) to get serious about enforcing their own laws.