I have been to South East Asia and married a women from the Thervada tradition. If it isn't a religion I don't know what that word means.

Yes of course you can treat it like a philosophy. You can pretty much do whatever you want. I am pretty confident I can treat 3rd wave feminist thought as a metaphysics system if I put my mind to it, I am also confident that I could interpret a child's drawing via a Marxist-Hegelian lens. Anything can be modeled as anything else. I can model the sun and the banana. Both appear yellow to me, both have dark spots, both make human life more enjoyable.

The issue is if that means anything, is it useful to us? So yes you can go thru their 25 centuries of writing spread over an area 3x of Europe, with 4x the population. Filter out everything you want and keep only what you want. Then slap a label on it called Secular Buddhism. You can do this, but don't really expect us to all say what you are doing relates at all to what they are doing.