A "mafia" of recruitment agents is trapping Myanmar migrants to Thailand in debt bondage despite a 2017 law meant to fight exploitation in the kingdom's notoriously shadowy job market, activists and workers say.Migrant labour - much of it from Myanmar - has propped up Thailand's economy for years, with foreigners working everywhere from factories to fishing boats, part of a global chain to produce standard supermarket items such as frozen shrimps, ready meals and pet food.