Would you assume this suicide was accidental because of his nudity? Was he engaging in an act of AeA?
Presuming no suicide note, an investigator would have to go on whatever other evidence was present. A hallmark of AeA is an escape route, i.e., some way out of the situation. With plastic this thin, the victim could just tear a hole in it. Until they went unconscious, of course.
Autoerotic Fatalities, by Hazelwood, describes such a case. However, key indicators were that the plastic had been torn and repaired with tape multiple times, showing that the self-suffocation was a repeated activity. There were also sexual magazines present, another hallmark indicating the victim's state of mind.
A third point is that self-suffocation using a plastic bag where the mechanism is lack of oxygen / build up of carbon dioxide triggers a feeling of suffocation due to the CO2 level. That's what gets some AeA folks off. If instead a gas (like butane) is used to displace the air, the build up of carbon dioxide won't happen, and so the reflex is not triggered.
If ones intention is suicide, this makes the process less distressing. Nitrogen or helium is certainly safer for those left behind; but they are harder to obtain, and a suicide may simply not give a damn about what happens afterwards.