A little better description of the thumping sound might help. Is it s consistent, steady thumping like a tire or an occasional thump or knock? If it's steady, then look at tire and/or wheel bearing. If it's a non-steady thumping it could be a loose shock, a loose body panel or a number of other things.
Dan & Ro with two Rescued Boston "Terrorists"
2015 Tiffin Allegro RED 38QRA
Previously '06 Itasca Sunrise 35A on a W22 Workhorse
'12 Jeep Wrangler Sport and/or '08 Honda Goldwing