To book the whole soft sleeper train for 2 person from Kunming to Dali, do we pay for 4 seats?

Hi, Lily. Since the Real-Name Train Ticket Policy in China implemented from Jan, 1, 2012, to buy the train ticket, people's valid ID card/ Passport should be provided. One people only have one valid ID card/ Passport, so he/she could only book one soft sleeper ticket once at one train ticket for this moment. You need to share one cabin with other 2 passengers.
Alternatively, you could book the deluxe soft sleeper ticket which is equipped with 2 bunks in one cabin, but it is more expensive than soft sleeper ticket.