Red Thai pepper vary from one-half to three inches long and one-fourth to one-half inch in width. Its smooth skin turns from bright green when immature to a vibrant red hue when fully mature. 

Its flesh has a meaty texture and encases many tiny seeds. It offers a potent, lingering heat registering between 50,000 and 100,000 Scoville units. When at the red stage the Thai pepper sometimes will have a delayed potency, the heat slowly building after consuming.