Thanks! I just found out there is a place to stay in Stung Trang:
There is a guesthouse in Stung Trang. Super basic, and half the people there don't know about it - there isn't even a sign. After getting off the ferry head north (right,) a few blocks past the main intersection and ask around. It's $3.
Chlong has a guesthouse too, and after that I'm pretty sure Stung Trang is the only place until you hit the highway.
We cycled for three month now. North Vietnam (too hard to start with), North Laos, Thailand, South Laos and now Cambodia!! From there to the south of Vietnam, up to the north again and then to China.
But our plans change by the day..