With fewer than 250 of these crocodiles left, the skin trade is driving the species not only to extinction, but also threatening the purity of its genes.
In February, Billy Kwan Kit-yue and Jason Lau To-hong, two environmental science students at the City University of Hong Kong, spent two weeks in Cambodia working with conservation group Fauna and Flora International (FFI) to study the threats facing the remaining wild crocodiles.
Their field trip was part of Ocean Park Conservation Foundation's University Student Sponsorship Programme, which gives aspiring conservationists a chance to consolidate their skills.
The students headed to the FFI headquarters in Cambodia's capital, Phnom Penh, where laboratory experts showed them how to examine DNA samples collected from wild and captive crocodiles.
It is common for commercial crocodile farms to crossbreed captive reptiles with their American relatives to produce finer leather and lower production costs. That is why scientists need to distinguish the crossbred crocodiles from the pure breeds, which are worth conserving.
In 2009, FFI helped to discover 35 purebred Siamese crocodiles in a local wildlife rescue centre. It has developed the first conservation breeding programme in the country.
The students also visited one of the many illegal farms where mistreated and poorly-fed crocodiles wait to be slaughtered.
Billy Kwan (left) and Jason Lau (right) with a conservationist during their survey of Siamese crocodiles in Cambodia.
These experiences led Kwan to question the ethics of buying luxury leather goods. "Do we have the right to crossbreed crocodiles for the sake of our endless demands? Should we allow crocodiles to suffer for our sake?"
Besides crossbreeding and hunting, crocodiles face another problem - the loss of habitat.
Cambodia's government plans to build hydro-electricity dams near Areng River, a rural area in southwest Cambodia, which is the world's most important breeding site for Siamese crocodiles.
Kwan says that the dam project will provide a stable flow of electricity, which is now available only from 6pm to 9pm. But if the project goes ahead, the low-lying areas where crocodiles nest and breed will be destroyed by floods.
"If there's a pressing need to develop rural areas to improve people's quality of life, compromises to the environment must be made," Kwan says. "Environmentalists can play an important role here. They can use their expertise to keep the damage to a minimum."
Toiling in the baking sun, the students worked alongside experts to estimate Siamese crocodiles' population in the Areng River area. They learned how to track the crocodiles' footprints, tail marks and excrement, and also record sightings of the smaller, freshwater reptile using a global positioning system.
"These scientific records help reflect the site's conservational importance," Kwan says.
The survey results proved useful when they joined another campaign to capture and relocate all the crocodiles living in O'Som, in western Cambodia, before a similar hydro-electricity project is constructed.
This "frontline" experience has helped equip Kwan, who is passionate about rainforests and wild animals, with the essential skills to continue his research.
It has also strengthened his desire to become an environmentalist, specialising in the protection of horseshoe crabs.