Mediates high affinity thiamine uptake, probably via a proton anti-port mechanism. Has no folate transport activity. H(+)(in) + thiamine(out) = H(+)(out) + thiamine(in) Optimum pH is 7.5. Widely expressed but most abundant in placenta, kidney and liver. The disease is caused by variants affecting the gene represented in this entry. Belongs to the reduced folate carrier (RFC) transporter (TC 2.A.48) family.