thong has 3 distinct synonyms spread across 3 of its 5 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
underpants resembling a G-string; worn by women especially under very tight pants
“she wore thongs in her quest for the callipygian ideal”
Synonyms, antonyms and the broader and narrower relations for thong come from Princeton University’s WordNet. Full sources and licences.
a thin strip of leather; often used to lash things together
minimal clothing worn by stripteasers; a narrow strip of fabric that covers the pubic area, passes between the thighs, and is supported by a waistband