The 18-year-old Youth Olympics silver-medallist notched up a comprehensive triumph over his 30-year-old Thai rival, who also happens to be an Asian bronze-medallist from the 2006 edition.
"In my first bout, my body felt a bit tight but it all turned out well in this bout. Now even my body feels good," the boxer from Assam told PTI from Astana, where he is competing in just his second senior international event.
Shiva had created quite a flutter by defeating a world champion in the finals in his debut senior international tournament, in Belgrade, where he went on to clinch a gold medal.
"I was aggressive and had worked hard on a plan. I saw his recordings from previous tournaments to prepare myself. I knew I could beat him and I am glad I did it," he said.
Shiva will now face Japan`s Satoshi Simizu, who beat Myong Il Kim of North Korea 23-10, for a place in the finals on Wednesday after a rest day tomorrow.
A win in the next round will assure him of a place in the London Olympics as well.
But in case he loses, he will have to pray for a gold for his rival as only the semifinalist who is defeated by the eventual champion will get the London ticket.
The Indian took a slender 5-3 lead in the opening round by being the "more aggressive" of the two boxers and worked to the same plan in the second round as well.