Well, I would be careful about wanting the "thai experience", for that is exactly what I sought and that disappointed me about training in Thailand. Unless you speak Thai fluently, and you are only and exclusively into fighting, you won't enjoy being surrounded by Thais only in some camp in the outskirts of Bangkok. I went to train at Sitsongpeenong (Bangkok) for a few weeks, thinking that its isolated location, its huge stable of Thai fighters, the lack of any distractions around the facility, would lead to the ultimate Muay Thai experience. It turned out, however, that mine was a foolish way of reasoning: the eastern outskirts of Bangkok became rapidly boring after a few days, the Thai fighters wouldn't really speak to me or any of the other students, while the trainers barely spoke a few words of English; it was impossible to socialize, and that, added to the fact that there was nothing in terms of distractions outside the training hours, quickly made my stay very different from what I expected. I learnt that distraction from training, as long as it is not intended as drinking and partying, is equally as important as training itself.
For what concerns Yokkao I can strongly recommend it.
Not only is the gym located in the heart of Bangkok, in a beautiful area in which you won't feel isolated, but the training and the vibe around it are great. The vibe, in particular, is what struck me most pleasantly: there is a sense of joy during training; everybody laughs, smiles, has a good time; you see Manachai smashing pads, Singdam coming back from his daily run, and Saenchai arriving at the gym looking for the first victim to prank. The quality of training is high, the level depending on your skill: I have seen lazy tourists doing the minimum required and professional fighters being pushed to their limit; you will have to show interest and motivation, for you will only get what you are willing to give. But no matter what, Yokkao has nothing deserving criticism. I had a private session with a trainer named Sak, and found him a great coach, highly experienced, patient and motivated. Please consider training with him if you are at Yokkao.
For what concerns privates with Saenchai, I recommend you to book them in advance and be ready to pay 200$ per hour. Saenchai is not only the legend of this gym, but also the head of it: it was my impression that the type of Muay Thai taught at Yokkao resembled very much Saenchai's style on the ring: clever, elusive, fun.
That would be it about Yokkao, but there is another gym I want to recommend to you, though it is located in Ao Nang, in the South of Thailand. It's called Khunsuek, it opened only recently and is a state-of-the-art facility. It certainly caters towards westerners but there is a trainer here, named Peteak Sor Suwanpakdee, who is by far the best coach I have ever had, who will tear your technique apart, and push you hard; one class with him is worth the entire trip to Ao Nang.
Hoping it helps, I wish you a good trip.