Usually if a word has been borrowed from another language (and doesn't have a synonym in the original language), it's a sign that the object or concept in question was imported into the culture from whatever language the borrowed word came from. I assume that the pencil was introduced to Thailand by English speakers due to the fact that their word for it transliterates to "dinso" (which, when properly pronounced, sounds an awful lot like the word "pencil" does when said by someone with a Thai accent).
The Thai word for "fire" is something that transliterates to "fie". Thai isn't an Indoeuropean language, and it's not possible that fire was introduced to speakers of the language by the speakers of some Indoeuropean language. And yet...it's so close! It's a word that definitely strikes me as being in the same family as pyr, pir, pu continumum of fire words. Any idea what gives with this one, Jonathan?