I recently stayed in Thailand for 3 months - looking for what you are looking for. It doesn't seem to exist. The Wats purely cater for their own. If you want to meditate, you are reduced to open touristy temples where at one time I opened my eyes to a Japanese tourist busy clicking away at me meditating! There don't seem to be any courses to take and Buddhism in Thailand I'm afraid has gone downhill. In my opinion the better Buddhist centres are now in the West. I saw Buddhists hitting defenceless animals, smoking, chatting up woman, eating and sending for takeaways in the evenings when they are not supposed to be eating and the higher monks seem to walk around with loads of cash. I'm sure there are good ones but it has really gone downhill from when I first went to Thailand in the 70's. The government asked a lot of Buddhist temples to take on the large population of orphans, and there is where I think the problem may have started. When you have people that don't choose to be monks it can only go down hill from there.
By the way I travelled all over, Phuket, Nong Khai, Sukhotai, Chiang Mai etc.