Thai food doesn’t make you drowsy at all. In fact, I think it has more of the opposite effect.
Foods that make you sleepy are usually high in saturated fat or simple sugars. In other words, unhealthy foods. But Thai food is good for you and does not feel heavy in your stomach.
Thai food doesn’t have much added sugar at all, but it does traditionally use white rice which is a simple sugar that breaks down quickly in the digestive system. This means that blood sugar will spike more quickly than with complex carbohydrates such as brown whole-grain rice that take longer to be digested.
But I tend to think that the spiciness and liveliness of Thai food perks me up more than makes me feel tired.