Big warning when crossing the boarder from Lao Cai to Hekou. You will cross and its a really short walk to the bus station. There is a man who works there, Tom. He might change his name, hes got a shaved head and a little bit darker for a Chinese man. Dont trust him, Don't talk to him, dont deal with him. Hes not dangerous but hes in it for the money. If you find a man named Knee you can change money with him at a decent rate.
Good luck, the bus ride to Kunming takes 9-12 hours depending on what bus.