Bangkok to Sihanoukville distance is about 653 km and it will take you around 16 – 22.30 hours to go to Sihanoukville depending on traffic and border crossing. The most popular way to travel from Bangkok to Sihanoukville is by bus. There are several companies operating this route such as Travel Mart. and Ticket Price 57 USD. It’s always recommended to book tickets in advance.
You can book bus ticket online on buscambodia.com