Why is Japan called a land of contrast?
When a traveler first encounters Japan, there appear to be two Japans: there is a Japan that exists now, not just modern, but post-modern, already shaping the 22nd century; there is a traditional Japan, the Japan of the flowering of Zen Buddhism, the arts and of the samurai warrior and the Shoguns.
There are two connections to the nickname, which is typically applied to Japan, not Thailand. The first is that the Japanese name for Japan (Nihon / Nippon) means "origin of the Sun." The other is that Japan, being east of the Asian mainland, was called the "land where the Sun Rises" in ancient China.