I suppose that depends on what you will accept as evidence. There have been several threads on ATS regarding Reptilians and underground life.
One thread I started shortly after joining ATS was Hollow Earth source of Alien
activity? Members posted a lot of information on that thread. I'm sure there are many other threads to look at too. Try using the ATS Google
search and look up key words like "Hollow Earth" and "reptilians". There is also loads of information outside of ATS also.
Also if you are interested you can help GrOuNd_ZeRo and join him with Reptillian Researchers
needed. I find researching is the best way to learn about a subject.