Revenue Watch Institute gave Myanmar its lowest rank in its latest report on transparency in the extractive industries.
Sanctions have eased on Myanmar as the country takes steps toward democratic reform. Human rights groups said sanctions encouraged reforms in the first place.
EarthRights International said it's been able to document how activity in Myanmar's extractive industries is tied to serious human rights abuses.
"Myanmar remains a high-risk area for foreign investment, and companies and their home states should take serious measures to mitigate the risk that their actions will contribute to internal conflict, human rights and environmental destruction, and corruption," the advocacy group said in a statement Wednesday.
The U.S. Office of Management and Budget in May said U.S. entities that have new net investments of more than $500,000 need to report on policies and procedures in Myanmar by July 1. The reporting requirements extend to human rights, corruption and any arrangements with security service personnel.
ERI says governments are "generally" backing economic engagement over human rights issues in Myanmar.