Difference between thermal reactions and photochemical reactions
Yes, you are right thermal reactions take place exclusively on the ground state surface, while a photochemical reaction takes place, at least in part  on the excited state surface. 

But there is another difference between them as
photochemical processes offer an advantage over thermal methods by forming thermodynamically disfavored products. Therefore, they overcome large activation barriers in a short period of time, and allow reactions that were inaccessible by thermal processes.