That Sanatana Dharma was spread throughout the world in ancient times.
This can be known if one understands ancient geography,when the landmass was different from what we see today,the excavations of Hindi Deities, Symbols from around the world.
From the descriptions of different parts world,geographical in nature,by Valmiki in Ramayana in detail in the Sundarakanda, Description of lands during Rama’s Aswamedha Yaaga in Yuddha Kanda; similar descriptions in eighteen Puranas.
Evidence of Rama in the middle East,
Rama, Dasaratha and Bharatha’s name in the Kings’List of Sumria,
Shiva Lingam in Mecca,
Hanuman, Makaratdwaja in Central America,
Vatican design as Shiva lingam with Avudayaar.
Trinetra Dance of Shiva in Australia,
Pharoahs with Thiruman,Vishnu Marks,
Rama Sita Festival is conducted. In Mexico.
I have detailed articles on these and more.
The spread of Sanatana Dharma towards middle East was more ancient and widespread.
Korean queen was from Ayodhya,India
The four Vedas are called Chatur Vedas there.
The customs of Hinduism are present in the Far East even today.
Teachers’ Day is conducted every year in Thailand as Guru Vandana Day.
It is called ‘Wai Khru’ .
Despite Buddhism shadowing over Hinduism there,the Wai Khru Festival refers to Shiva, Narayana and uses Akshatha,puffed rice on the occasion.
And this festival is celebrated on Thursday, Guru Vaara, which is the day of Guru,Brihaspathi.
‘TThe wai khru ceremony (Thai: , pronounced ) is a Thai ritual in which students pay respects to their teachers in order to express their gratitude and formalize the student–teacher relationship. It is regularly held near the beginning of the school year in most schools in Thailand. Wai khru has long been an important rite in the traditional martial and performing arts, as well as in astrology , Thai Massage and other traditional arts; students and performers of Muay Thai and Krabi Krabong, as well as Thai dance and classical music, will usually perform a wai khru ritual at their initiation as well as before performances to pay respect and homage to both their teachers and the deities who patronize their Arts.
Reference and citation, including Image of Students.