Hi, I go to Hanoi then take a train to Nanning, how can I apply Chinese Visa at Hanoi or anywhere?

You can apply for it from the consulate general of PRC in Hanoi. If you go to PRC for tourism purpose, you should prepare those documents containing the filled-out application form attached with a passport-sized color photo, your passport and copy of its data page, round trip tickets and hotel booking record, travel itinerray, income certificate and travel insurance (if required). And then submit the application to the consulate general of PRC to apply for the tourist L type.