In my experience, the Thai restaurants around me (East coast US) like to make their sauces very oil/butter heavy, which contributes to the second phenomenon you alluded to. I've never been to Thailand, so I don't know if this is an exclusively American phenomenon or not.
I personally really like a good Lat na, but what I'm served is often noodles in a thick, chicken flavored grease (rather than stock or gravy).
I personally really like a good Lat na, but what I'm served is often noodles in a thick, chicken flavored grease (rather than stock or gravy).