From Kampong Cham there is a dirt road connection (mostly in good condition) along the Mekong. Take road 223 up to Stung Trang where you can cross the Mekong by ferry to continue on road 308. That way Chlong is about 70 km from Kompong Cham. Share taxis to Chlong don't run along the Mekong but use NH7 and then road 73.
With the improvement of the roads, fast boats along the Mekong River between Kratie and Kampong Cham no longer run on a scheduled basis. Alternatively you might find a slow (cargo) boat that can drop you off at Chlong.
There is a ferry service over the Mekong.
There are two guesthouses in town. One is next to the market. The second one is a few hundred metres from the market just off the street to Kratie.