I live almost an hour away from the nearest public Olympic-size swimming pool, so it’s not exactly convenient, but according to @Thonged4Life, thong swimwear is permitted there.
Unfortunately, thongs still aren’t allowed at my regular pool. The policy simply states, “swimsuits are required,” so it’s not impossible that it could change, but the management has asked that only “full-bottom” swimsuits be worn in that area because they expect complaints.