Muay Thai styles are usually cut rather tight but always have an elastic waistband. This one is a Thai size L (92-96 cm  hip circumference), reason why I marked it as Medium.

Made of high-quality satin.
Suitable for training and competition.
Made in Thailand, the motherland of Muay Thai, in one of the oldest Thai shorts factories.
These are new, as I broke my hand and never did Muay Thai again.