Clinton met Friday with Myanmar's President Thein Sein as she wrapped up her visit to Cambodia to attend a summit for the Association of Southeast Asian Nations.
With some provisions, U.S. President Barack Obama this week signed an executive order authorizing U.S. investments in Myanmar.
Myanmar's president, through an interpreter, said he was "very pleased" bilateral relations with the United States were improving.
"We are pleased that Obama eased the sanctions," he was quoted by Bloomberg News as saying.
Watchdog groups expressed grave concern over the decision, however, pointing to government corruption and ongoing human rights issues in Myanmar.
Clinton, for her part, said the easing of sanctions didn't come free of expectations.
"Promoting economic activity in this region requires more than just encouraging businesses to invest and trade," she was quoted as saying. "It also requires creating and defending the conditions in which economic activity can flourish over the long run."