That's part of my school's uniform, so I don't do this on purpose. I don't really know when it shows through my khaki pants, but when I see him laughing I go check and I see it lol. He usually tell the guys when that happens and they laugh while staring. Why does he do that?
Thongs do not leave panty lines (or so they say) but I do know that there are a lot of panties that have AND advertize that they have no panty lines (all cuts. Bikinis, Boy Shorts, Briefs, even "Granny Panties"). So why not but a three pack of them?
If you like the attention flaunt it. Some guys might see it as trashy though. He's just being cocky drawing attention to your ass. You could most likly sleep with him if you want. If you don't like the attention change the brands up a bit and when he makes commits retort with you wish or never gonna happen. Lol