Having ridden often in Cambo, for the last 10-years, below are my most recent suggestions for Sihanoukville accommodations:
As a "Cheap Charlie", I recent years I've normally stayed at the Boston Inn, which was opened in 2007, near the CalTex gas station, in downtown Sihanoukville: A/C, refrig, TV (w/ UBC), doublebed, no HW for $10-US.
Non 'Cheap Charlies' should consider either the Small Hotel (around the corner from the Boston Inn), with A/C, HW, TV, wifi, an excellent restaurant and attentive staff for $25 www.smallhotel.info], or the Beach Club, a fairly new place located on the inland side of the 2nd street back from Ochheuteal Beach, with A/C HW, TV, wifi, safe a large pool, and attentive staff. It offers a nice breakfast buffet for $5-US/150-Bt. www.beachclubcambodia.com]. The latter is highly recommended!