I might consider ALG World the ultimate in extreme language learning and seems by far the best method there is. ALG stands for Automatic Language Growth. This is total immersion and no translation. So you start at Level 1 with no knowledge of the language and the teachers only speak in the target language. Notice that they have 2 teachers, not just one. I think that it is best to have 2 teachers in the classroom. 2 native speaking teachers. Since you start out not knowing the language, the teachers use more than just speaking in order to communicate to you. So you are understanding. You are not trying to remember words and not being asked to speak in the target language. You are just acquiring the language. Your ability to guess is what facilitates your acquisition of the language. This natural acquisition gets you native fluency. That means you speak with the facility and pronunciation of someone who grew up speaking the language.
In a way, this seems similar to an English lesson at a conversation school in Japan because the native English speaking teachers here (in Japan) cannot all be expected to be able to speak Japanese so therefor the lessons that students take at one of these "schools" is all in English. Therefor I would like to point out what some of the differences are. First and foremost, here in Japan, you get only one teacher teaching a lesson. At ALG World there are 2 teachers in the classroom. Having 2 teachers provides natural interaction and dialog for the students. With only 1 teacher, the teacher has a much bigger challenge to display the natural language. The next point is that at ALG World, the students are not under any pressure to produce output. In Japan, progress is measured by output. The pressure and stress to speak is quite counter productive. I know I can perform better and remember things more easily when I am not under any pressure. The last major difference I would like to point out is the number of hours. At ALG World, the students take class for 6 hours a day. So that would be 1500 hours in a year and could be 3000 in 2 years. The average student may take 1 or 2 hours a week of lessons in Japan. So it could all just be the number of hours. But the difference between the approaches shows up in pronunciation and facility in the language, not just the number of years it takes.
There are some videos on YouTube. This one is a Japanese lesson at ALG World.
I don't know which level that class is, but I can understand it 100%.
Here is a level 1 Thai lesson. Very interesting. It seems to me that in Thai some sounds are made with the whole mouth. It's like the sound is not just being pushed out but it is being held in the mouth. Obviously I can't describe what I mean or what I hear. But it just feels like the sounds are produced in a totally different way. Maybe it's not just some, but maybe all the sounds. I noticed this also in the movie Ong Bak. I bought this movie in May or June this year here in Japan so I've got the original Thai as well as a Japanese dub and Japanese subtitles.
If you want to know more about the ALG method, there is a presentation on YouTube divided into six parts. The first part is here.