Two notes: First, some of the religions (Alawism, Alevism, Druze faith etc.) are often classified as sub-groups of Islam, but sometimes classified as older gnostic religions dissimulating as Islam. Dr. Michael Izady, whose great maps I used for the Middle East, argues for the classification as pre-Islamic religions who need to dissimulate as Muslims to avoid persecution.
Second, in Asia, it is often impossible to map the religions as it is usual for people to follow two or more religions (such as folk Shinto and Buddhism in Japan or Confucianism, Taoism, and Chinese folk religion in China). Therefore, some religions "share" a colour. China is based on this recent map. In North Korea, the largest religion seems to be Korean folk religion, closely followed by Cheondoism (a syncretic religion based on Korean religion and Confucianism). In South Korea, I included all provinces with Christianity as largest religion as Protestant. In all of these provinces, Protestantism was larger than Catholicism, however, in some of these Buddhism was larger than Protestantism alone.
Generally, the level of detail varies. For some countries, only province-level information or only rough estimates are available. For other countries, religion data is available down to every village.