I am thai citizen, what document should i actually bring to apply a Tourist visa in bangkok.

In general, you need to provide your valid passport, an application form, a recent taken photo, your hotel bookings and round trip tickets for application based on the rules.
However, if you have a bank statement, you are suggested to provide to show that you have enough money to cover your expense in China. With the bank statement, it may be easier for you to get the Tourist L type.