What do you wear under your thai shorts?
I'm just wondering since I'm a beginner and I have yet to wear thai shorts because I don't know what to wear under them for I fear that my genitals might slip out at any given moment. Thanks.
Some of our guys wear Thai shorts for grappling, they wear the lycra (I think Americans call it spandex?) MMA shorts underneath, I expect lycra cycling shorts would do the same job. It's important to wear something close fitting underneath, not just for modesty but because you will wear a groin guard at some time too, that needs to stay in place.
Thai shorts allow a great amount of motion hence them being short.
I would suggest any comfortable and that doesn't restrict motion. Almost anything except boxers. Wear boxer and you will be flashing every one.
That is one brand among others suitable to wear under your shorts. You can check around with similar brands too and decide which would match your preference (and your budget). UnderArmour can be pricey, but the quality is very good.