The law has received widespread criticism from international and local communities.
The two-day training came as Cambodia approved a measure to tighten controls on Cambodian migrant laborers.
The draft law contains 85 articles meant to reform the prison system, but it does not touch on military prisons.
Some of those same NGOs have given their support to a highly public land dispute over a development project at Boeung Kak lake.
Villagers say their livelihoods there are being threatened by continuous government concessions to private rubber and other companies.
More than 100 villagers from rural areas detained by authorities in Phnom Penh after handing out leaflets detailing land concessions.
The garment sector provides around 300,000 jobs and more than $2 billion a year in exports.
Prime Minister Hun Sen signed a subdecree giving 1,000 families still living near the lake approximately 12 hectares of land.
Some 4,000 families are expected to be pushed from the Phnom Penh lake, which has been filled in almost to completion by Shukaku, Inc.
Former refugees at the congress said they wanted to share in the freedoms they were given.
The Diamond Bridge stampede was the worst disaster in Cambodia’s modern history, leaving 354 dead and 393 seriously injured.
Cambodia exports labor to Japan, Malaysia, South Korea and Thailand especially.