I am now in She Oo Minh Meditationcenter in Myanmar and want to continue Satthipathana in Tahiland. Ambhavan sounds interesting. But i want to stay open end and longer time than just 4 weeks, maybe a few months. It that possible there?
I suggest you make enquiries at the Embassy of Thailand with regards to obtaining a religious visa. The embassy officials should be able to assist you with what you need. Having gone through the process of attempting to get a religious visa to Myanmar, I can tell you that there is some paper-work involved and processing takes some time.
All the best with your plans.