@Wayne ********
yes, I'm one of those. But we're talking about different things. One thing is being a French national applying in Vietnam with a French passport issued in France and a different thing is a French national applying in Vietnam with a French passport issued by the French embassy in Beijing or Bangkok. Under any of those two scenarios is possible to apply and get the visa. The issue arises however on what or how to input that info in the application. When the passport on my example was issued at Bangkok, some would input that it was issued in Thailand, while some that it was issued in France, both scenarios with different results.
In my specific case, I used a Costa Rican passport issued in Seoul, Korea, to apply at the Thai Embassy in Seoul. On place of issue I wrote Seoul, and had no problem getting the visa. Some people argue that you must "always" write the country name, so issued in Costa Rica, not in Seoul. I didn't do they way, but each Embassy might have a different opinion on the matter.
I always recommend just to copy paste whatever is written on the passport itself. My mother applied recently (online) at the Thai Embassy in Santiago, Chile, which has the jurisdiction over Costa Rica.
Her Costa Rican passport, issued locally, stated three letters and three numbers as the "place" of issue, something like "BCR-264". We just copy pasted that on the application, and her visa was also approved last week.