I have found Indian food most spicy and my favorite.

I ate all of the above and more, I think that the Marocan is the spiciest of all.

Mexican food really isn't that spicy and hot. They sometimes ADD hot things to their food at the table, but not in the dish itself. Thai food can be blisteringly hot but usually you cook it to how the person wants it. I love mine really hot. My husband more on the medium side. When we eat it out, very often they will ask you how hot you want it and give you a number scale, usually 1-6, 6 being hot. Indian food comes all sorts of ways. I think it is more spicy than just hot. And they have raitas with each meal to help cool things down and lotsw of bread. Not much, other than fresh herbs and greens cool down Thai food.

Mexican food!

IMHO it is Indian/Pakistani food. Ofc it all depends on who is cooking and what. Some dishes from other places will obviously be spicier than others, but for the spiciest food possible, Indian/Pakistani can not be beat. Also, I rate Jamaican food spicier than Mexican food.

In US, they can all be equally spicy (hot) - Korean, Indian, Mexican, and Thai. But having lived and traveled overseas, this is my experience: Keep in mind, when we say spicy in US, we mean hot. For Indians, hot is hot, and spicy means a lot of spices. In India: Indians tend to snack on a side dish of small green chili peppers like they were carrot sticks while having their food. You can sit down with a group of Indians to a self-serve buffet style lunch where all the items being served in trays are both spicy & hot - Not a single dish is not hot. The food is so hot, as an American, I immediately get the hiccups after a few bites. But the funny thing, though the group of Indians can eat green chilies raw with no problems. When we go have Korean soup with red chilies in it (There's a lot of Korean restaurants in Delhi), I can manage to eat the soup, though sweating, and the Indians think it's too hot. Thailand: One bite of the food and I can't eat anymore, it's that hot, full of red chilies in everything they eat. And the cooks make it even hotter for the local Thais compared to a foreigner ordering it. I had a friend bring a buddy from Mexico on the trip, even the guy from Mexico couldn't believe how hot the food was and he said he likes it spicy. To Summarize: India and Thailand are very close on the spicy (hot) list, but Thailand has a slight edge. Korean food is slightly ahead of Mexican food in the spicy (hot) department, but I can't say that it is hotter than India or Thailand.

Spice volume is not so important to me. After I got used to spices enough to consider the flavor as a whole I can say I often prefered Thai food. However Indian dishes hit the spot when the time comes...The Malay version of spice presentation gave me a new take on ways to mix flavors. Now nowhere can I get Kim Chee the right way than Korean....Horseradish hits a higher note than peppers. I wouldnt want peppers on Sushi. I guess naga jalokia is the hotest pepper so if ya need to turn the heat to max throw one of those in whatever ethnic dish you have in front of you.

I love Korean food.