I live in an affluent suburb of Bangkok. There is a much used walking path (really a low traffic loop of city streets) very near to where I live.
I walk there several times a week. Maybe half of the walkers say hello. About a third of them introduce themselves, ask my name, ask after my well-being etc. In general they chat and joke with me as far as their English proficiency allows.
There are some who I thought standoffish until I said hi to them first and then they turned out to be friendly.
These are largely retired folks and from all appearances well-to-do if not wealthy.
There is only one out of about 30 regular walkers who seems to feel superior (at least it seems that way).
These are people who could easily look down on me as a foreigner, they may not be HI-SO but they are definitely not low status individuals.
So my thinking is that just like anywhere, xenophobia, snobbishness, and maybe just a desire to be left alone exist but are certainly not universal among Thais.