The Collaborative International Dictionary of English v.0.48:

threads \threads\ (thr[e^]dz), n. pl.
   Clothes; clothing; as, he was wearing his new threads at the
   party. [Slang]
   [PJC]

WordNet (r) 3.0 (2006):

threads
    n 1: informal terms for clothing [syn: togs, threads,
         duds]

Moby Thesaurus II by Grady Ward, 1.0:

36 Moby Thesaurus words for "threads":
   apparel, array, attire, bedizenment, clothes, clothing, costume,
   drapery, dress, dressing, duds, fashion, fatigues, feathers, fig,
   garb, garments, gear, guise, habiliment, habit, investiture,
   investment, linen, rags, raiment, robes, sportswear, style, togs,
   toilette, trim, vestment, vesture, wear, wearing apparel