
He died Friday evening after battling stomach cancer in Singapore General Hospital since January 31, his daughter said.
Myint Thein had been active in the Burmese democracy movement since 1988, when mass anti-military demonstrations first rocked the isolated, formerly socialist state, ending in an army-led bloodbath that claimed up to 3,000 lives.
Since winning a parliamentary seat in the 1990 elections, he had been detained several times without trial, including a three-year stint between 1998 to 2001.
As a close aid of NLD leader, the Nobel peace prize laureate Aung San Suu Kyi, he was named the party's spokesperson in 2004.
He was last detained in Rangoon's notorious Insein Prison on September 27, 2007, after the peaceful protests led by Buddhist monks ended in a brutal crackdown.
Myint Thein's health deteriorated while he was in detention and he had to be hospitalized upon his release on October 30.
"He was formerly healthy and strong. Frequent detentions and lack of medical treatment and inadequate food in prison made him sick and infected some diseases," said Aung Din, executive director for the US Campaign for Burma.
After being diagnosed with stomach cancer, authorities permitted him to fly to Singapore for treatment in January.
Deutsche Presse-Agentur