I sometimes see people complaining that their local Thai restaurants won’t make dishes really up to the “Thai spicy” standard.
There is a solution, which is common in Thailand itself: Prik Nam Pla. In Thailand, this is probably the most used table condiment – essentially, Thai chilies in fish sauce, so a salty and spicy dip (basic version, things like lime juice, shallots, garlic and sugar can also be added). If your Thai dish isn’t hot enough, drizzling some on is most effective way to increase the heat – it is better than adding things like Sriracha, which can completely change the taste balance of the dish.
If for some reason, your Thai place won’t provide it and/or you’re eating at home, it is super easy and fast to make ([example recipe](https://www.delish.com/cooking/recipe-ideas/a37418787/prik-nam-pla-recipe/)).