Greeting from The Battambang Bike!
So sorry for being lately reply! but I have the great pleasure to receive your inquiry! No, you don't need to book long days before just one day or once you arrive in Battambang.
my friend and I booked the tour online a day in advance. however when we went it was still considered low season. I would consider booking a couple days in advance depending on the season you plan to be there.
It really depends on the season - in general yes, book in advance, but there's one tour on Saturday or Sunday that's open for everyone and also free.
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