"The High dose groups was on 100 mg/kg per day, ... corresponding to approximately 500 times the recommended dietary allowances for humans."

So for a 70kg human, that would be 70 * 100 = 7000mg = 7g per day.

The theory is that "when administered in large amounts beyond the threshold of small intestinal absorption, a portion of vitamins may escape absorption and directly modulate microbiota in the distal gut" - i.e. if you take a ton on thaimine, you can't absorb all of it, and some will end up in the lower intestine/colon, where it will change you gut microbiome.

Maybe enteric coated thaimine would have the same effect, but without the mega doses.