When you are in Sapa and want to get to Loas you can book a ticket at different shops. We booked ours in the Hao Lan hotel. (also named Diamond Hotel / barbershop, hairsalon) They can offer you a busticket between for $22. We also visited other places and asked around but this was the most cheap bus we could get to Loas from Sapa.
Bus from Sapa to Laos
There is one bus on the way to Laos and that one will go at 18.00. Ours arrived “little” later 18.45. So we could get in a little later. We booked our ticket to Muang Khua. We want the boat on the river to go further south. You can also go with the bus to Luang Namta and Luang Prabang. The bus was fully packed! I think for 25 sleepingseats there where at least 50 persons in the bus. The people where all over the bus. On the floor, behind the last seats in the luggage space, averywhere. The luggage has to be on on top of the bus. With the fog I was happy that I had my raincoat for my backpack. (the drivers putted another plastic sheet over the luggage as well) The bus was stopped by the police once the organisers paid money and we could go further.
Bordercross Sapa in Vietnam to Laos
Just before we crossed the border we split up in smaller busses. Ours was fully packed again. The luggage was on top again but the weather was nice! the bordercross from Vietnam to Loas was quite easy. You only had to pay. First for the sticker $37. (different per country) after that the second window ($2) for the tourist fee. Third window $3 for the stamp to get in. In total for me as a dutch guy the visa for 30 day costs $42 US.
Arrived in Muang Khua
After 17.hours we arrived in Muang Khua. We met a couple from Spain and told us about the boat options to the south from Muang Khua. The little town Muang Khua itself is nice. Little restaurants small market and a nice bridge over the river!