Anonymous participant here is how I would have handled the situation. Q) When the immigration officer is annoyed about my handing over the visa when he did not ask for it A) apologize for the mistake because it is his country and I have to show respect to officials. Q) When asked about why I got the DTV in Vietnam A) Give the actual reason I was in Vietnam and be prepared to show evidence of my activities there. Responding that "someone said I could get a visa in Vietnam" doesn't answer the question. Having then realised he was getting annoyed about his issue with process you then decided to avoid answering his questions. Then you anonymously complain on facebook and start justifying your behaviour. All of which means you are hiding things and using them to provoke other people.
Anonymous participant you're asking me how to reply simply when your first comment clearly stated that you gave no explanation whatsoever as to what you were doing in Vietnam. All your previous explanation states is your legal entitlements to apply for the dtv there and no explanation as to why you were actually in Vietnam. As someone who used to work in government- skirting around questions is immediately suspicious. Never underestimate peoples ability to get upset about surprising things and don't expect too much.
With the DTV I did get a couple of questions, which I haven't usually had before. I answered very concisely with one word answers and I get the sense immigration officers were just checking that what I said matched with what was on my DTV application. Avoid any additional rights based "because I can" statements because sounds like you got a "because he can" response back.
Anonymous participant i haven't seen software activity mentioned. I'm guessing you mean soft power activity? Would also suggest there would be certain course specific expectations within those soft power activities. The point I make is really that the stronger your own intention the less you may experience other people's intentions. Which I think can only be a good thing...
In my opinion is better to just fulfill the requirements of the visa and be thankful you don't have to stress about your status. Otherwise just go for the 2 visa exemptions and do want you like.
Interesting given the land entry is unlimited how does someone show evidence of their intention to leave Thailand within the 60 days? My understanding is that the criteria for the visa exemption is a flight out. Does this now mean a booked train ticket would be ok?