Today we cannot imagine Indian or Thai food other than spicy/hot. But if chili was introduced in this region only after Europeans conquered the Americas did the cuisine of these regions undergo a massive change in taste or were the people there relying on other sources of spiciness?
Not to discourage any further answers but I recommend you look at these older answers on Asian cuisine prior to the Columbian Exchange:
Hot peppers originally came from the Americas, but India, Thailand, and large parts of China are famous for their spicy foods. How did they arrive, and how long was it before they became an integral part of the cuisine? by /u/CongregationofVapours
And there's a great book that covers this and many other similar questions. 1493 by Charles Mann. Highly recommend!