When it comes to thongs, the fabric can make or break them especially if you are at the beginning stages of wearing them. Really the fabric can make or break any pair of underwear. I would argue more so for thongs with fabric in a place you aren’t used to. You want to make sure the tail of the thong is made of a fabric that will be comfortable. It’s going to be sitting between the cheeks all day.
What should you look for in the fabric? I’d say how soft it is and a lighter weight fabric. If the fabric is lighter in weight then there will be less fabric between the cheeks. Soft fabric is always something good to have all the way around. Who doesn’t want something soft against the skin? Ideally, you’d want to be able to touch the fabric to figure out which you think would be comfortable in the back. Unfortunately, it isn’t common to find a thong at the store unless you are lucky enough to live near a men’s underwear store. You’ll most likely be ordering online, so it won’t be realistic feeling the fabric of the thong. Now how do you decided on what fabric to look for in a thong that you can not touch? First, you could go by underwear you already own. You already know which pairs are soft and lightweight in your underwear drawer. Look at what they are made of and look for a thong made of it. Another option is read reviews and look for ones that talk about the comfort of the fabric.
Some of the fabrics I think would be good options to try are bamboo, knit silk, and modal or micro modal. The modal and bamboo fabrics are usually blended with another fabric like lycra for some elasticity. For me, thongs made out of these fabrics can go as unnoticeable between the cheeks. Some lace and mesh fabrics can be scratchy, so you’ll want to avoid those for now. If one fabric doesn’t work for you then try some others. Once you find a fabric that is comfortable for long term wear, you can start experimenting with other fabrics.