On a recent trip (Thong Pha Phum in Kanchanburi province) I met three Thai geologists who had a stack of maps These where high-quality 1:50.000 maps and they had comments written in them. Thus I have experimental proof that there are four Thai who can read maps (the three geologists and the person who made the map), and can assume that the dark figure is much higher.

As a counterexample, a friend of mine recently got a globe as a gift. To test him, I asked him to point out Thailand on the the globe. He worked his way all around the globe (arbitrarily jumping from one place to another and reading the country name to me) and after 5 minutes, he found Malaysia, and when I realized he is not aware that Thailand borders somewhere on Malaysia, I gave up and said goodbye and left. You could blame alcohol, he was a bit drunk.