Finding genuine non discriminating employers of Qual Eng Lang Teachers

Have you looked at VUS, ILA, British Council? They're the top centers in Vietnam. As for discrimination and stereotypes you will have to get used to that since they are part of the Viet's culture.

After reading both your post and profile, I suspect that you are suffering from age discrimination which is a very real thing in the ESL industry in Vietnam.  As your report that you have been in Vietnam since 2014 you certainly have been employed but apparently the experience has been less than you expected.

I was 63 when I came to Vietnam and was turned down by several schools including some that interviewed me and even more that never responded at all to my application and CV.  In retrospect, I am glad some of them turned me down.  Although I did not teach for long, like you I hold a BEd which is the basic teaching credential in the US.  I was fortunate to find a school that hired me and when I left three years later, did not want me to go.  The two best teachers at this school were retired teachers, one from the US and one from AU.  Both of them worked almost exclusively in public schools because they provided the most hours in one place and because they were comfortable in that environment.  Non teachers were not and had more hours at the center.  In any interview situations, you should emphasize your potential staying power and willingness to work in one place longer than younger candidates will.  You surely have classroom management skills that can make you a valued employee.