Choosing the right thermal shirt or top for hiking or camping is important to maintain comfort and body temperature. Here are some tips:

• Material: Choose synthetic fabrics, such as polyester or polyamide, or merino wool. These materials are great for thermal insulation and breathability, and they dry quickly.
• Layers: Choose shirts or tops that can be used as part of a layering system. The base layer should be fitted to the body to help regulate temperature and moisture.
• Fit: The shirt or top should be comfortable, but not too tight. Make sure it allows freedom of movement and does not cause chafing.
• Seams: Look for shirts or tops with flat or seamless seams to avoid chafing during long hikes.
• UV protection: If you will be hiking in the sun, choose shirts or tops with UV protection to protect your skin.
• Weight and compressibility: Choose shirts or tops that are lightweight and can be easily folded or rolled up, making it easier to carry in a backpack.
• Additional features: Check to see if the shirt or blouse has features like zippers that allow for ventilation or sleeves that can be adjusted.
• Style and comfort: Be sure to choose a shirt or blouse that you find comfortable and that matches your style, as this can increase your motivation for outdoor activities.

Trying out the shirt or blouse in action before purchasing is always a good idea to make sure it will meet your needs during the activity.