The website describes that Fox released the first Thai heavy rock song in Thailand.
One of Fox's members has become the well known heavy rock singer and another the popular heavy rock dj and also the manager of the Thai underground heavy rock band "Fresh and Skin".
There was not many band which play the kind of music like that in the wide range of Thai music market.
From the
http://progressive.homestead.com/THAILAND.html, it mentioned about some traditional music from north western Thailand, the others are the 60's dance pop rock (like The Shadows) mixed with the Thai pop songs.
I understand that this "Thai Beat" music was not the mainstream music of the Thai music market at that time. It was like dance club music only.
I have just time for the quick view at the refer website and answering your question so just a Thai man opinion, I hope it could make you have a clearer view.
bye.
polotoon
www.wikipedia.com search for caravan thai band