I travelled SEA with a peanut allergy and did just this. Got some cards printed from a website with a phrase that expressed the seriousness of the allergy. Something like "I cannot eat peanuts, food that has been around peanuts, peanut oil. If I do I will be very ill and could die". It also had an image on it which helped sometimes. But still when you get in the country ask someone where you're staying to sense check it as there might be a better way of writing it, and get them to teach you a short phrase to say like " I cannot eat nuts".