I have always worn a thong under my riding pants. I don't own anything else so I don't have much of a choice! They are fine! I must have a pretty good liner in my pants, too, because I don't wear shorts, and I hadn't even thought about it before. Do you ladies just wear plain old spandex/cotton ones? Like the short aerobic-type ones? Is that comfortable? I may have to try that, just to see if there is a difference.
But, yes, thongs are fine. And I don't think anyone can see a thong through riding pants! But then, I have never ridden behind me before......hmmmmmm....