The market opens at 7AM and close 11:00
Go as early as possible as it becomes crowded by midday. It officially opens at 7AM but many vendors, particularly those selling food, have already opened their stalls but 6AM. However the best times to go are early in the morning before most visitors arrive. Get to see the stall holders eating the bowl of breakfast noodles from the floating noodle shops of the market!
By 9am it will be crowded and there may be “boat traffic jams” which delay your trip.
By the middle of the day it will also be hot as the hot Thai sun which is so nice on the beach is much less fun when sitting on a boat in a khlong with no wind.
Majority of international tourists arrive by coach after 9AM so if you are earlier than this you will see more of the real Thai side of the market as the visitors will mostly be local Thai people.