Thais used to be animist before Buddhism was introduced. They worshipped trees, rivers and other natural objects. While Hinduism has been mixed in with this, it helps explain certain water festivals and trees with ribbons wrapped around them, especially at the site of car crashes. Trees are said to be inhabited by spirits.
It is therefore not a leap to understand why Thais see auspicious things in plants or other natural objects, or even car numberplates following a crash. Superstitious origins for everything.
(Before anyone feels this is superstitious rubbish, try understanding that there are still some billions of people who believe in somebody rising from the dead after three days and people riding winged horses.)