Affordable Care Act for US citizens residing abroad

I am a US citizen but I have been living in New Zealand for the last few years. From what I understand, US citizens residing abroad are exempt from participating in the ACA, and I really do not know much else about the ACA. I am currently back in the US for a couple of months, and I have been offered some temporary work as a substitute teacher. However, there are some forms included in the paperwork that I was given which relate to the ACA. I am concerned that once I register for it I will have to carry that responsibility even when I return to New Zealand where it will be of no use to me as I am covered under the NZ national healthcare service. I have heard about penalties for not registering etc, and if the US gets the impression that I now live permanently back in the country because I am working here I could end up being penalized later. I am not sure that all of this is worth it for approximately 1.5 months of work. If anyone know how this would work, I would like to hear it.

Thanks