I HATE riding in a thong, it always seems to go places a thong should not go.
I like to wear seamless panties. Victoria Secrets makes seamless panties that stay in place and are very comfy. The Body line has a seamless line and the Incredible also has some nice ones too. I wear these under yoga pants too and there is no VPL.
Going to join the VS crowd, only I'm not sure you can get my favorite pair anymore. I haven't seen it in stores in a while. They are a silky material, sort of boycut, with only one seam which is vertical down the back. Not only do they have no VPL, they also don't have that death seam underneath that kills me in certain saddles.