Myanmar, known formerly as Burma, embarked on political reforms, starting with general elections in 2010. Since then, the United States and other governments have eased sanctions on Myanmar.
Phil Robertson, deputy director of Asia affairs at Human Rights Watch, said praise for the former military junta should be balanced.
"Burma's reforms over the past year are hindered, not helped, by international oversell and hasty praise in the face of continued serious human rights abuses," he said in a statement from Bangkok.
While democracy doesn't develop "overnight," he said, the country still has mounting rights challenges ahead.
The government recently lifted bans on public gathering, though some lawmakers there expressed concern that certain Internet restrictions remained in force.
Robertson said Washington and its allies need to address lingering concerns in Myanmar like political prisoners and ensuring accountability for alleged war crimes.
"Foreign governments should recognize that Burma's history shows that a tough response to rights abuses doesn't derail reform but promotes it," he said.