I run most mornings and have been over every country lane, farmyard, riverside path up to 10 K distance. Depending on how I'm feeling ( I always give them a SWK) I might shout it out if they don't answer, or ask if they speak Thai. I think that everyone around here, mostly farmers, knows about this bizarre behaviour, I now get kids that I didn't see shouting 'Hellooo' at me.
More annoying is when I see a Farang also exercising and he won't say good morning. I get to talk English with an Anglophone about once a month.
In the remote mountain, Swiss village I used to live in, people (not all) would get worried and stop their car, bicycle, walk to ask what was wrong if I didn't answer their greetings.
Anyway, the above remarks refer to country people; city people don't count.