I would use a cotton thread if you’re considering putting it in the microwave. Anything synthetic could melt. I don’t ever put ours in the microwave – they stay in the freezer.

What kind of thread should you use?

You probably can, but you want to be careful. There is no moisture in the rice or fabric, so they can catch fire easily. Also, you want to make sure you use fabrics and threads that will perform well in the microwave – anything synthetic or metallic could be dangerous.