The double negative tricked me! It has been a long time since it tricked me, but I thought it meant "I don't plan to never work" (which is an odd sentence, of course).
Does this express the intent of the speaker to literally not plan on going to work anywhere; or does it refer to the speaker still going to work in places, but never planning the method of the work?
My first impression is that he plans to not work anywhere.
but it can be read as amibiugous, if it's a prophecy or something.
Well, but what does it mean? As double negative generally isn't correct in English... (although ok, I was told that this here kinda works but it's definitely informal)
Yes it is double negative, it might be a sarcastic answer from a person to parents who are nagging them about their lack of finding a job.
Well, as the literal translation is actually correct in Polish... it's hard to say. To convey the sarcastic meaning, I could probably say "Nie planuję gdzieś pracować" (which is then actually correct English if translated literally), or maybe "Planuję nigdzie pracować/pracować nigdzie" (I plan on working nowhere). But all those versions seem to me very strange, they would rather be confusing than funny.
In most English dialects, that means, "I do plan to work somewhere"
In some dialects, such as AAVE, Appalachian English, and most Southern AE dialects, it is a common way to say, "I do not plan to work anywhere"