Catholicism was not the dominant religion it was Buddhism.
Buddhism
Cambodia.
The Asian nations where Buddhism is a major religion in China, Japan, Vietnam, and Sri Lanka. It is also a major a religion in Thailand and in Nepal.
East Asian religions = Buddhism and Taoism South Asian religions = Hinduism, Sikhism and Islam
Almost all the south Asian countries follow Buddhism. In China also, it is the largest religion leaving the atheist.
There is no one main religion, its different throughout the various countries, and even then, its different through the various regions of that country. Religion in Asia ranges from Buddhism, Shintoism, Islam, Hinduism, Christianity, plus countless of other religions.
Buddhism
At least 4 religions. Two of the prominent ones are Buddhism & Confucianism.
Buddhism is the predominant religion in the majority of southeast Asian countries and Islam is also widespread but only two countries have Catholicism as their main religion, the Philippines and East Timor.
Although often seen as an Asian religion, Buddhism is practiced almost everywhere in the world
I'm not pretty sure but i think that it is Buddhism... hope it helps :)