Anyone arriving early for a retreat, wanting to stay longer or arriving during retreats is welcome to stay, initially for up to seven days, at the main Suan Mokkh monastery. If, after seven days, you intend to prolong your stay, you need to get permission by the abbot of Suan Mokkh or his representative. Permission will readily be granted to dedicated meditators and students of Buddhism. Doing a chore (community work like sweeping leaves) while staying is part of the practice. Reservation is neither possible nor necessary. Just show up and find the information desk inside the monastery. Please do not arrive after dark.Accommodation in dorms (for men) or individual rooms (for women) is free; food is available inside the monastery or at the nearby stalls. There is an excellent library with books in many languages as well. Please note that there are neither organised activities nor a certain schedule to be followed, no teachings or instructions been offered while staying at the main Suan Mokkh monastery. This possibility is therefore most suitable for people who have done a retreat at the International Dharma Hermitage already or for experienced meditators who can use the wat's facilities without guidance.
So if you show up on November 1st or later and they won't let you into the retreat (and you never know, they might even though the website says definitely not), they will almost certainly allow you to stay at the monastery and then join the December 1 retreat. You'd have to practice on your own until then, but boy would that allow you to really hit the ground running when the retreat starts and then you could stay on afterward and practice by yourself some more at the monastery since you have 2 months. As long as you are a sincere student who is really there to practice, they will take care of you.