I have been visiting Cambodia for many years, and am now living in Siem Reap for almost one year. Apart from being a freelance translator, I also am a partner in a small travel agency in Siem Reap.
I can cover the requested topics. What we need to discuss further is the size of each of the three articles and the level of detail within each. Personally I would concentrate on the tourist aspects of the different destinations, but keep the part on restaurants and accommodation very limited, perhaps referring to other sources - unless you're a travel agent that wants to cash in on commission. Hotels and restaurants change over night, in ownership, in quality, and even in existence. Hence this is an extremely timely topic. For example, I have been in Sihanoukville about 4 months ago, but would need to visit it again to give meaningful and current information. By the time you publish the material, it could again be out of date. Better to pick a few long-standing businesses in each category (budget, middle and high end) and refer your readers to up-to-date reference sources, such as TripAdvisor.
Regards,
Alfons