Non-coherent　chaotic　communication　has　gained　increasing　attention　as　it　provides　an　efficient　solution　for　reliable　communications　without　requiring　channel　state　information.　In　this　paper,　we　propose　a　non-coherent　reconfigurable　intelligent　surface　(RIS)-empowered　differential　chaos　shift　keying　scheme　with　two-level　nested　index　modulation　(RIS-DCSK-TLNIM).　In　the　proposed　RIS-DCSK-TLNIM　scheme,　the　reference　index　and　information　index　are　nested　to　form　two-level　nested　index　modulation.　This　design　enhances　both　the　spectral　efficiency　and　bit　error　rate　(BER)　performance　of　RIS-DCSK-TLNIM,　albeit　at　the　expense　of　slightly　increased　complexity.　Furthermore,　we　propose　a　joint　detection　algorithm　to　recover　the　information　bits　transmitted　via　the　reference　index,　information　index,　and　two　distinct-mode　signals.　We　then　extend　RIS-DCSK-TLNIM　into　an　enhanced　system　to　achieve　higher　spectral　efficiency.　Subsequently,　we　analyze　the　BER　performance,　spectral　efficiency,　and　system　complexity　of　RIS-DCSK-TLNIM,　and　compare　these　metrics　with　those　of　benchmark　systems.　Comparison　results　demonstrate　that　the　proposed　RIS-DCSK-TLNIM,　when　configured　with　a　small　number　of　time　slots,　can　achieve　more　than　twice　the　spectral　efficiency　and　at　least　a　6　dB　gain　in　BER　performance　compared　to　benchmark　systems.　©　2002-2012　IEEE.