Do anime/cartoons count as well? I haven't had much luck seeing thongs in TV series in general, and movies is kind of the same thing, apart from a couple "comedy" movies that I've forgotten. But there's a Japanese anime/cartoon I've been watching called Jojo's Bizarre Adventures, admittedly, I honestly don't know/understand the whole plot of the series actually, but there was several episodes featuring these 3 sort, "main" villains called the "Pillar Men", supposedly over a thousand years old, and are supposedly "gods" even though they are built like Adonis's, heh. But everything they do, and anything surrounding them, just gave off a rather homoerotic feel to it, and there was one scene that definitely had caught my attention which featured them not wearing most of their armor, and well, picture speaks for itself.
I know two of them doesn't look exactly like thongs, but close enough. Also an interesting side note is, that two of the character's names are namesakes of two music groups, Wamuu, being related to "Wham!" and also sporting a haircut kind of similar to George Michael's back when he was younger, and Edisii, which is AC/DC.