The conceptual evidence that Hinduism was already in existence during pre-vedic period can be pointed to Hindu deities in China, Korea and Japan.
It is fact to everyone that after Chinese civilization, Korea came to exist and from Korea, Japan.
In the same way the influence of Hindu God moved from China to Korea and then Japan.
But the question is how did the Hinduism or Hindu God entered China?

To my best of knowledge so far, i fail to see any Brahmans priest entering China from India or Nepal in teaching about Hinduism to the Chinese before 18th century or earlier?
Yet to my knowledge that the some of the Hindu deities are found in oriental countries since earlier than 6th century needs to be NOTED.
So what's the link behind this.
Well here's some information regarding this:

China (Cinaratha) in the Epic of Mahabharata:

           It is well known that in the Mahabharata the Cinas appear with the Kiratas among the armies of king Bhagadatta of Pragjyotisa or Assam. In the Sabhaparvan this king is described as surrounded by the Kiratas and the Cinas. In the Bhismaparvan, the corps of Bhagadatta, consisting of the Kirtas and the Cinas of yellow color, appeared like a forest of Karnikaras.
The reference to their wealth of gold, silver, gems, sandal, aloewood, textiles and fabrics clearly demonstrates their association with the regions included in Suvarnadvipa. Thus, the connection of the Kiratas and Cinas is a sure indication of the fact that the Indians came to know of the Chinese through the eastern routes and considered them as an eastern people, having affinities to the Kiras, who were the Indo-Mongoloids, inhabiting the Tibeto-Burman regions and the Himalayan and East Indian territories in Assam and Sikkim.

In early Indian literature China is invariably shown to be connected with India by a land-route across the country of the Kiratas in the mountainous regions of the north. In the Vanaparvan of the Mahabharata the Pandava brothers are said to have crossed the country of the Cinas in course of their trek through the Himalayan territory north of Badri and reached the realm of the Kirata king Subahu. The Cinas are brought into intimate relationship with the Himalayan people (Haimavatas) in the Sabhaparvan also. The land of the Haimavatas is undoubtedly the Himavantappadesa of the Pali texts, which has been identified with Tibet or Nepal. In the Sasanavamsa this region is stated to be Cinarattha. Thus, it is clear that China was known to the Indians as lying across the Himalayas and was accordingly included in the Himalayan territories. In the Nagarjunikonda inscription of Virapurusdatta, China (Cina) is said to be lying in the Himalayas beyond Cilata or Kirata. These references to the proximity of China to the Himalayan regions, inhabited by the Kiratas, show that there were regular routes through the Tibeto-Burman territories, along which the Indians could reach China.


Henry Rudolph Davies (1865 - ) says that Besides Buddhism, Shaivism was also popular in Yunan as is manifest from the prevalence of the cult of Mahakala there. This ancient Indian colony in the south of China was the cradle of Sino-Indian cultural relationship for a long time.

Therefore this clearly points out that Hindu god was already in existence even before the Rig-Veda came into existence. The Kiratas and Cinas intermingled to the point that they fought the Pandavas as ONE army. The point of one's culture influencing others could not be denied. Hence the  religion(Hindu) of Kiratas were taken in by Cinas(Chinese).