nudist with undergear fetish
Exceller is wearing an Ikingsky thong. They are available on amazon of all places and quite inexpensive. I have several and they are quite comfortable, seem to be well made and come in a good array of colors. Good all day thong that gives you a little lift without crushing.
I chickened out of buying a Hom thong brief for my wedding day in the early'90s when they were briefly ;-) available in department stores, but bought my first one soon after followed by a swim brief. These days, it's thong or string briefs all the time except for medical appointments or for when I go commando. Men's ones are no longer available in shops, but women's ones can be fine depending on the style and then the rise of internet shopping allows for all tastes anyway.
I love the swim ones but rarely have an opportunity to wear them, although perhaps I should be more bold. My other swim briefs can be quite small anyway for places where a bloke in a thong may be challenging to others.
As for disguising what's underneath, that varies. My blue '90s Hom string is quite conservative in that respect, my Koala ones often less so.