Depends what your definition of "rag" is. Classic ragtime - a la Scott Jolin and others - employs a classical thematic format. Typically: A-A-B-B-A-C-C-D-D. The Maple Leaf is a fine example.

In the folk & blues world, "rag" can be anything the composer wants it to be. "Rag, Mama, Rag" is a typical example from the band; "Rag Mama Blues" is (I think) a Blind Blake offering (someone will correct me if I'm wrong here, I'm sure!). "Feel-Like-I'm-Fixin'-To-die-Rag" is an offering from Country Joe - but based largely on the old jazz standard "Muskrat Ramble"...

Depends on how severe you want to be with the definition!