I would definitely say the Ming Empire in China. At least during the early 16th century, before a period of instability, the Ming had by far the largest economy, population, and army in the world. The Empire supported a army of over 1 million soldiers, while the total population was estimated between 175 to over 200 million. Its also worth mentioning that almost all of the silver mined in the Spanish colonies made its way to China, where it was used as common currency.

Ebrey, Patricia Buckley, Anne Walthall, James B. Palais. (2006). East Asia: A Cultural, Social, and Political History. Boston: Houghton Mifflin Company.

Brook, Timothy. (1998). The Confusions of Pleasure: Commerce and Culture in Ming China