Lack of funds and available workers have slowed attempts to restore forest cover in the heavily logged country.
Local authorities had forbidden Christians from neighboring villages to join each other for festivities, a local source says.
Two valuable caches are uncovered in one week, suggesting the trade will be difficult to shut down.
The ceremony marks the fifth anniversary of the abduction of Sombath Somphone.
Signs posted at a major crossing warn would-be migrants against being lured into servitude by false promises.
It has now been five years since the rural development expert vanished in police custody.