
Lightweight Commercial Sewing Kit
Simple commercial sewing kits can weigh less than 1 gram.

Needle Threader
If you have a hard time threading a needle, you may want to carry a needle threader in your kit. Needle threaders typically weigh around 0.5 grams.

Safety Pins
There are so many uses for safety pins that every sewing kit should have at least one. Safety pins weigh a fraction of a gram. The safety pin pictured weighs 0.1 grams.

Dental Floss
You can use dental floss as thread in an emergency. However, dental floss doesn’t have the strength and properties as high quality thread.

Nymo Thread
I recommend Nymo thread for anything that requires strength. For instance, adding stitching to a backpack strap. This is because Nymo thread is a nylon monochord, this means it is a single bonded strand. Normal sewing thread is composed of multiple filaments. As a result these filaments can break more easily. Nymo thread was originally created for the use in the upholstery industry and is generally much stronger than normal sewing thread.

DIY Sewing Kit
I think the ideal sewing kit is the one you can make yourself. You can select the type of thread, colors and thickness that match your specific needs. This simple DIY sewing kit was made from a business card, needle, extra thread, safety pin, and a needle threader and it only weighs about a gram. The sewing kit pictured would be a good sewing kit for a day hiker. A more advanced kit with different types of thread, a spare needle, and extra safety pins would be better for a longer hike or backpacking trip. This is because the chances are higher that something will need repair.
Summary
I think every thru-hiker should make their own sewing kit to reflect their personal sewing needs. Hiking without a sewing kit is not recommended.