The below excerpt from "Revolution 2020" by "Chetan Bhagat"
The background story is as follows. One village in India is suffering with some diseases and villagers belongs to that village are dying due to those diseases. The below conversation between a villager and his son
'Baba, will I also die?' Keshav said, his voice a mere thread.
'Stupid boy. What nonsense,'the farmer said.
Here what is the meaning of a mere thread in this context?
Mere: used to emphasize how small or insignificant someone or something is
Thread: (1) a long, thin strand of cotton, nylon, or other fibers used in sewing or weaving. (2) a thing resembling a thread in length or thinness, in particular:
Question here: How can voice can compare a thread?