The Mekong Delta is a huge region, and this trip covers a surprisingly varied range of landscapes: abundant rice fields and hills, cosy canal paths.
While the terrain is flat as a pancake, the climate can be strength sapping, so keep that in mind.
As much as possible I’ve mapped out routes away from main highways, favouring shady smaller paths that bring you up close with local life.
It would be completely fine to ride this route in reverse, starting in Vinh Long or Sa Dec and finishing in Ha Tien.
Since Ha Tien is a short ferry ride away from Phu Quoc Island, doing the trip in reverse would also give you the option of adding a few beach days on to the end of your trip.
Map
Day-by-day route guides
Day one: Ha Tien to Ba Chuc
https://ricepedals.com/mekong-delta-bike-tour-ha-tien-to-ba-chuc/
Day two: Ba Chuc to Chau Doc
https://ricepedals.com/ba-chuc-to-chau-doc/
Day three: Chau Doc to Gieng Island
https://ricepedals.com/mekong-delta-diy-bike-tour-day-three/
Day four: Gieng Island to Sa Dec
https://ricepedals.com/gieng-island-to-sa-dec/
Day five: Sa Dec to An Binh Island (Vinh Long)
https://ricepedals.com/sa-dec-to-an-binh