no invitation letter, no plane ticket and no hotel reservations.

I am travelling from Hong Kong to Shenzhen by train. The train leaves Hong Kong ever hour. I have no plane ticket nor hotel reservations. I am taking a day trip. Can I apply the tourist L type with multiple entries for 10 years with no plane ticket, hotel reservations and invitation letter? If I am staying with a relative in China and going by train, what kind of document do you need?