I spoke with the (German) abbot of Wat Pah Nanachat a few days ago when he popped in for a visit. The scene there at the moment is not so easy for him as there are many junior monks and novices to take care of, and only a couple of reasonably senior experienced monks (12 Rains or so) to guide them. They are also unduly burdened by administrative issues like visa renewal etc. Now most of the monks are not at WPN but in Dtao Dum, a retreat place in the jungle on the Burmese border (for the hot season). 30 temporary novices from the local village will take over WPN for a few weeks soon, as a way of introducing them to the monastic life (this is an experiment only). You will have a chance to use the well-equipped library at WPN, but it will mostly be self-study with the exception of the Vinaya classes and some Sutta classes. Pali is something that those interested study by themselves. There will be some instruction in Thai language as well (mainly during the Vassa).
Then there is another associated monastery called Wat Mab Chan in Rayong, see www.watmarpjan.org
, where about 8 Western monks live and one can also ordain there under a Thai teacher.
I am not so well informed about the other places outside the Ajahn Chah tradition, though there are some in the Dhammayut lineage which might be good. Some big Mahanikaya temples in Bangkok might also offer more opportunities for study (but if you ordain with the Dhammakai group, they won't later accept you at WPN, you would have to disrobe and re-ordain).