Hi Alan,
From Can Tho to Chai Doc, you will be transported by a bus and the journey will be approximately 3 and a half hours long. There will be a toilet stop where necessary. Once you arrive at Chau Doc you'll travel by boat over to Phnom Penh and this will take approximately 5 hours.
We don't offer any other routes other than those stated, unless you decide to tailor make your holiday. If you give us a call, we can have a look into the options for you.
Kindest regards,
Monty