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 the town of Mahachai, home to Thailand's largest population of Burmese migrants, thousands of Myanmar's downtrodden crowded around her and chanted: "Long Live Mother Suu!"

"I had only seen her on TV and in newspapers," said Saw Hla Tun, who left Myanmar's Karen state seven years ago and earns a meagre wage carrying heavy salt sacks on his back. "I couldn't hold back my tears when I saw her."

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.

Suu Kyi arrived in Thailand on Tuesday night on a trip that shows just how much life has changed in her homeland. The Nobel Peace Prize winner lived 15 of the last 24 years under house arrest and dared not leave during the intermittent periods of freedom because she feared the then-ruling military junta would not allow her to return. Now an elected member of Parliament, she will speak later this week at the World Economic Forum on East Asia.

She'll return to Myanmar briefly before heading to Europe for a five-country tour in mid-June. She'll address the British Parliament, formally accept her 1991 Nobel in Oslo, Norway, and be the guest of honour at a Dublin tribute concert organized by U2's Bono and others.

Fixing a battered economy is one of the most crucial challenges facing Myanmar as it begins opening up in the wake of 49 years of military governance that ended only last year.

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

Andy Hall, a migrant expert and researcher at the Institute for Population and Social Research at Thailand's Mahidol University, said the Myanmar migrants -- up to a million of them lacking work permits -- make up between 5 and 10 per cent of the Thai work force, contributing as much as 7 per cent of the nation's GDP.

Many are exploited and paid reduced wages. Some have been trafficked; some have had their passports confiscated by employers. Hall said they were nevertheless "the lifeblood of a lot of the Myanmar economy, sending home money to support families who don't have enough money to eat."

"They have no voice, they can never speak up or stand up," Hall said. "So for Aung San Suu Kyi to visit is like a dream come true, someone who finally may be able to bring attention to their suffering."

One of the migrants, a 26-year-old woman named Khin Than Nu, works at a Thai canning factory and dreams of her home in Myanmar's Mon state.

"We left our parents in Burma, and all my brothers and sisters work here to support our parents," she said. "I hope Daw Suu will help develop our country, and bring jobs so we can go home."