When the party disintegrated after the Wa rank-and-file revolted against its leadership in 1989, he headed one of the largest breakaway factions, the National Democratic Alliance Army.

Mong La became an autonomous zone and his well-equipped private army of several thousand men retained its arms.

By the early-1990s Sai Leun headed one of the most powerful drug syndicates in northern Burma with an output of one to two thousand kilogrammes of pure heroin annually.

[7][8] Sai Leun made a few abortive attempts to develop traditional business interests in the city.

Sai Leun's construction business, Asia Wealth Company, has built a new sealed road that links Sop Lwe to the outside world.