I have just joined a gay social networking and news media site for men in Asian called Fridae.com - one of their tribes (discussion groups) is the Nudist and Naturalist Networks. Here is what I added to several responses concerning: Where in Asian can a guy go to a nudist beach?
In Japan, there are only two places where guys (mostly gay men) go as a nude beach (one in Chiba, and the other is a deserted spot on Shonan Beach). Neither are well known by the general public partly because they are so hard to find, and far from Tokyo. Also, it's not like Black's Beach or ones in other Westernized countries, people get naked very discreetly even on a supposedly nude beach. They generally wear swimwear when walking around or when in the water, but remove their clothes while lying in the sun.
The next best thing to a nude beach then is a hot springs resort or a public bathing spa, the latter of which there are over 50 in Tokyo. In these, men and women have separate bathing areas. Often, there is a small outside areas (enclosed by a fence for privacy) where the naked men can soak in a pool of mineral waters or lounge naked or draped in a towel. Inside, there are various types of baths, but the men are usually totally naked when walking to and from each pool and when they sit on stools at individual showers for washing body and hair. Many of them have wet and dry saunas.
However, you don't have to go far from any metropolitan area to enjoy the same atmosphere of men enjoying being naked. Formerly, there were the old-fashioned public baths or 'sento' in every neighorhood, which have just about disappeared these days, being replaced by large, more modern and luxurious: bathing resort (or 'onsen' - hot springs bath or spa).
The water has a higher content of minerals, particularly sodium (salt) and it's either brought in or created, but in sometimes comes naturally from the ground as Japan is a set of volcanic islands, also prone to earthquakes, as everyone knows.Well... for those in Malaysia or Singapore, and other places where there are not naked places, you can do what I often do: Make your own nude beach by just getting naked where the general public cannot see (easily).
In my trips to Thai, Singapore and Malaysia, I can recall a few places where this might happen, such as Sentosa Island, or a bit further afield - take a ferry or boat to one of the Indonesian islands not far from Singapore. There are surely some deserted beaches as well along Malaysia's southern coast, perhaps on Tioman Island (as there are plenty of foreigners), and also in East Malaysia (Sarawak), I was able to get naked inside the Bako National Park both inland and at any of many deserted beaches. Guides on individually hired boats can take you to a certain point, and pick you up later.
I realize that an important element may be missing when you simply go out and get naked alone. One of the most fun things about nude beaches is not only about being seen in the nude. It's also the chance to see others (especially men) in all their naked glory. You can't always do both at the same time. There must be places and events where men in various Asian countries are naked or dressing / undressing so take advantages of those spots even if you can't be naked yourself at the same time.