There is a few things worth considering when buying Muay Thai shorts.
Of course size is important, you want enough room to kick and knee with no restriction. Keep in mind a lot of Thai brands tend to be smaller than western sizes but most have a chart with waist measurements to help you find the best fit for you.
The lower quality materials can become see through when you sweat but a higher quality satin will ensure you don’t have that problem. Another thing to take into account is the fancier graphics tend to cost more.