In my opinion Marx's views on Asia were not very enlightened. They are heavily influenced by Orientalism and Eurocentricism whilst combined with plain ignorance of various Asian societies.
Marx on China which is a collection of articles he wrote on China for the New York Daily Tribune from 1853-1860 consitute pretty much all he wrote on China. In these he tends to stress the "stagnation" of China and its supposed inability to develop under its own power. He homogenises the Chinese as sharing inherent characteristics and then homogenises further by lumping the Chinese in with other "orientals" such as the Indians and Persians. Thus looking at his views on India and Persia in other works gives an indirect insight into his views on China. He ultimately argues that the Orient
needs Western imperialism in order to jolt it into capitalist development as it is otherwise too stagnant and backward to be able to do it itself.
Needless to say this view is very outdated and should not be considered theoretically plausible.