You do use those for the Thai Dessert called Ruam Mit (in english, it literally means "Mix Everything Together").
I don't have a recipe, but this is how you make it-
Boil the tapioca shreds in water, then when they're soft like spaghetti, drain them out using a strainer.
You then heat up some coconut milk, and palm sugar together, mix it all up, then put the strips in a small bowl and pour the sauce over it. Then you put some ice on top of it and eat it.
It's like a sweet soup, (a little too sweet for me
Here's some pictures on how it's supposed to look: