In this article, for any ring R with A⊆R⊆C, we describe the structure of the R-algebra of Drinfeld modular forms M(Γ0(T))R (resp., M0(Γ0(T))R, the ring of Drinfeld modular forms of type zero) of level Γ0(T) and the structure of mod-p reduction of Mp0(Γ0(T)) for p≠(T). As a result, we are able to study the properties of the weight filtration for Mk,l(Γ0(T)). Finally, we prove a result on mod-p congruences for Drinfeld modular forms of level Γ0(pT) for p≠(T). © 2022 Elsevier Inc.