MAHACHAI, Thailand - Myanmar opposition leader Aung San Suu Kyi, on her first foreign trip in nearly a quarter-century, offered encouragement Wednesday to impoverished migrants whose flight from their homeland is emblematic of the devastation wrought there by decades of misrule.

“Don’t feel down or weak. History is always changing,’’ she told an exuberant crowd of thousands southwest of Bangkok. Many held signs saying, “We want to go home,’’ and Suu Kyi said her visit was aimed at learning how she could help them.

“Today, I will make you one promise: I will try my best for you,’’ she said.

In Mahachai, home to Thailand’s largest population of Burmese migrants, thousands of Myanmar’s downtrodden crowded around her and chanted: “Long Live Mother Suu!’’

After speaking to the crowd, Suu Kyi met with migrant workers who told her they are mistreated by employers but don’t know their rights and have no legal means to settle disputes.

Fixing a battered economy is one of the most crucial challenges facing Myanmar as it begins opening up after 49 years of military governance.

Thailand hosts around 2.5 million impoverished Burmese who have fled here to work low-skill jobs as domestic servants or in manual labor industries like fisheries and the garment sector.