In the last century between 3.5E (~1372 DR), and 5E (~1489), Thay went through the civil war in which lich Szass Tam won, and banished other wizards making necromancy and undead arcanist the ruling class of the nation.
In 3.5E Thay was famous for two exports – slaves and magic items. However, in the current situation of the world creating magic items is more difficult, and Thay going full necromancy shouldn’t be so interested in the exports.
This connects with enclaves which they were building in distant countries in the Sword Coast. If I remember they even appeared in one of the offical adventures for D&D 3E. I can’t find any materials which confirm that they are still there, but if they can’t produce and export magic items they don’t make too much sense.
Is there any mention in the books or other official materials for D&D 5E that Thay Mages still are selling magical items in the enclaves, or are they abandoned?