Thomas comes into the pack, after last week featuring in the Guinness PRO14 clash at Glasgow Warriors.
Lock Joe Davies is also called up, to partner Matthew Screech in the second row.
The final change sees Calvin Wellington named on the wing for the final home fixture in the opening six rounds of the competition.
Meanwhile, Iwan Burgwin, Taylor Hansen, Dan Babos, Garin Price, David Richards, Rob Brookson and Joe Goodchild have been released out to Principality Premiership clbs this weekend for game time.
Dragons A (v Leinster A):Carwyn Penny, Calvin Wellington, Tom Hoppe, James Benjamin, Deon Smith, Jacob Botica, Rhodri Davies; Josh Reynolds, Rhys Lawrence, Chris Coleman, Joe Davies, Matthew Screech, James Thomas, Lennon Greggains (c), Taine Basham
Replacements: Zac Hewlett, Scott Evans, Luke Yendle, Max Williams, Ben Fry, Dafydd Buckland, George Gasson, Will Kelly
