Dear Khanapot Raksee,
Thank you very much for booking ticket with us. I am so sorry since King Express is fully booked on December 4 for route Lao Cai to Hanoi thus they cannot accept your reservation. Would you mind considering to take Chapa Express train for the alternative. This train is one of nicer trains to Sapa, departing from Hanoi is same as King Express and included shuttle bus complimentary to Sapa town. We do offer ticket cost is $40/ticket/way.