The company, which operates 2,800 stores around the world, released a list of its suppliers last week in an effort to boost its standing as a responsible corporation through transparency.
"H&M wants to contribute to a more transparent and ultimately more sustainable fashion industry," the company statement said.
The Phnom Penh Post reported Monday that some of the suppliers have had rocky management-employee relations in recent years and two have been the site of mass fainting incidents.
Hundreds of workers fainted in 2011 on two separate occasions at one supplier's plant in Kampong Chhang province, the Post said.
In 2012, at the same plant, 3,000 workers went on strike demanding improved work conditions.
At a second supplier in Phnom Penh, 100 workers fainted in a 2011 incident and 50 more fainted in a separate incident this past February.
A 2011 strike at a plant in the capital city that was prompted by the firing of union members turned violent, the Post said.
The head of the Cambodian Legal Education Center said the H&M list would be "very helpful."
"Now it will be clear. If we find a factory producing for a vendor, we will know if they are [working] as a subcontractor for H&M," said Moeun Tola, the head of the center.