The throw was nearly four metres further than that managed by second placed Kentaro Nakamura of Japan, who threw 72.04m.
Rana was not the favourite before the competition as his personal best until then was 68.94m, which he had managed at the Junior Federation Cup in April this year.
However, he surprised everyone at the Thai Japan Bangkok Youth Center with the throw of the competition. Vikas Yadav claimed the bronze medal with a throw of 68.65m.
Yadav though missed out on a Youth Olympic quota with only the top two athletes winning places for the Games.
Earning the other quota along with medals was Bamhane.
With the top three athletes of the race earning qualification for the Buenos Aires Games, the 15-year-old from Maharashtra claimed a silver medal in the women's 1500m race in 4:25.66 seconds.
She finished behind Yuki Kanemitsu of Japan, who clocked 4:24.21 seconds, while Guiping Zhang of China was a distant third with a time of 4:30.45 seconds.
Bamhane's time was the fastest of her career, bettering the 4:36.61 seconds she had clocked at the Junior Federation Cup in April this year.
Narrowly missing out on a quota place for Argentina was hurdler Aparna Roy, who fell short despite managing to set a new personal best with a time of 13.98 seconds to claim a bronze medal in the 100m hurdles, which was not enough in the end.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)