I didn't actually mean structured in that sense. Just that you can target particular areas that you miss completely in pure immersion, especially if you're struggling. You don't need to follow some kind of typical language book syllabus. Plenty of ways and methods to spend time with a teacher focusing on the areas that you want and need for your own use. A teacher can help you make sense of things going on around you - but if you need/want that might also depend on how knowledgeable and patient the people around you are when you want to ask questions. I'm self-taught, never had a formal Thai lesson, and got to a level where I can take on corporate translation work. I reckon I would have got a few short cuts from taking classes in my earlier days.
It's probably quite a few years since I read up on language immersion research and projects so would appreciate some pointers about papers to catch up on. Results were very mixed from what I remember on much of the earlier research.