Which country is the second most populous in East Asia?

Which country has the largest population in Africa? Which country has the largest population in Europe? Which country has the third-largest population in Southeast Asia? What is the most populous country in South Asia, excluding India? What is the most populous country in South Asia? What is the most populous country in Oceania? Which country has the third-largest population in South America? What is the second most populous country in Southeast Asia?