A pig is traditionally associated with Nang Songkran Raksot.
Raksot is the daughter assigned to Tuesday in the Nang Songkran tradition, and her symbolic mount is a pig. Traditional Songkran almanacs connect each of the seven daughters with a particular animal, along with other attributes such as food, posture, and the hand holding her father’s head.
These associations are part of the folklore surrounding Thao Kabinlaphrom and his seven daughters. The daughters carry his head around Mount Meru in a rotating annual ceremony, with the weekday determining which daughter and set of omens applies.
The animal is symbolic, not a reference to a standard festival parade animal. Modern Songkran processions may feature many kinds of decorative imagery, while the Raksot-pig association specifically belongs to the traditional Nang Songkran classification.