Shiva Thapa entered the quarterfinals of the World Championships in Almaty, Kazakhstan today beating Argentina's Alberto Melian in the 56kg category. The 19-year-old reigning Asian champion beat Melian in a split decision of 2-1.However, former cadet world champion Thokchom Nanao Singh bowed out of the event after losing his pre-quarterfinal bout 0-3 to eighth seed Anthony Chacon Rivera of Puerto Rico in 49 kg category.