My Kru is certified under him. He was an experienced fighter beforehand though, and most of his students are competing in amateurs with a winning record.
I think he just got it so he had something to show
Are thai gyms associated with Chai Sirisute reputable? I think he started the USA Thai Boxing Association.
I have no direct experience with Chai, but what I have seen some of his certified instructors teach looks nothing like what I have seen in the camps in Thailand. I think many of the instructors blend JKD or something into their Muay Thai.