Crochet yarn and thread

Which do you prefer, yarn or thread?
Crochet is quite popular in my country. You will easily find your yarn or thread, but the variation of them, however, is not much. Vietnam has a tropical monsoon climate, so we usually do not use the thick and fuzzy yarn for crocheting as temperate zone. Especially in Ho Chi Minh city, where I am living, the hot climate is mainly, so thread is preferred. I really love many different kinds of yarn and thread in the other countries showed on internet, but it's so hard to find in Vietnam.

My cotton thread collection:

And the tough thread usually used for making bags:

I also use some kinds of cotton yarn for sweaters, scarfs and hats...