Ramad in Khmer language means rhinoceros. Ramad is a Himapan creature which derived from an actual animal. In the old times, Thai traditional artists probably didn’t know how a rhinoceros look like because they never saw one, so they draw a ramad based on what’s been described in literature, resulting Ramad to look like a tapir (having a flexible trunk like snout).

It was known to Thai people about how an actual rhinoceros look like when a baby rhinoceros was sent to King Rama V. Since then the practice of drawing a Ramad with tapir like snout was discontinued.
 
Most likely the species of tapir which was used to represent a ramad is Malayan Tapir, a species of Tapir that can be found in the Western region of Thailand. Ramad is also a mean of transportation for one of the Hindu gods, Akkanee (God of Fire).

Akkanee or Agni, Hindu God of Fire is one of the most important of the Hindu Vedic gods. He is the god of fire, and much of his importance comes from the role of fire in sacrifices and rituals. As the fire which consumes the offerings to the gods, he is seen as the mediator between heaven and earth.