I have written on the presence of Sanatana Dharma in the South East,Far East, Malaysia, Indonesia, Vietnam , Laos, Cambodia, Korea, Japan, Australia and New Zealand.
Another piece of evidence that Sanatana Dharma was present in the South East is that the Secondary flag of the Thai King Rama IV, had the mount of Indra, Chief of Devas,Airavata , white elephant.
The flag also had the Hindu sacred symbol OM.
‘King Mongkut (Rama IV) felt the need to create a Royal standard to distinguish his royal barge from other vessels during his many travels around the Kingdom and to fly above the Grand Palace in Bangkok when he is in residence. In 1855 a Royal Standard was created called the ‘Thong Chom Klao’ (ธงจอมเกล้า
‘However the sight of an empty flagpole when the King was not in residence at the palace was considered inauspicious, therefore a second flag was ordered to be hoisted during the King’s absence. This Flag is called the ‘Thong Airapot’ (ธงไอยราพต), the rectangular red flag depicts a mythical three-headed white elephant (Airavata) in full regalia standing on a golden base with a golden pavilion on its back. Within the pavilion is the Thai symbol for Aum or Unalom. The elephant is then flanked on two sides are two seven-tiered Royal Umbrellas.‘
Reference and Citation.