AFAIK high population density was a pretty common thing in Chinese history. Plus their bureaucracy kept decent records and probably could compare economic and social outcomes between periods with more and less people per unit area. Well, so did any premodern Chinese thinkers propose population control as government policy? E.g. to borrow a page from Malthus, maybe they could have proposed paying lower class women to marry later (maybe after the age of 22) to reduce overall fertility.
I don’t believe there was any idea of population control as government policy, except for the standard “peasants die from war and famine”.
Something to remember, too, was that in the premodern world, population growth was generally seen as a good thing.