Any process that stops, prevents, or reduces the frequency, rate or extent of the chemical reactions and pathways resulting in the formation of thiamine.
Synonyms:
exact_synonym:
down regulation of thiamine biosynthetic process; downregulation of thiamine biosynthetic process; negative regulation of thiamin biosynthetic process; negative regulation of thiamine anabolism; negative regulation of thiamine biosynthesis; negative regulation of thiamine formation; negative regulation of thiamine synthesis