Many people are surprised to learn that Thai food does not contain much soy sauce. People assume that because it is an Asian cuisine that it must be heavy on soy.
While Japanese and Chinese food both make liberal use of soy sauce, Thai food does not. Instead, Thai food employs fish sauce, which is another dark and salty sauce similar to soy.
Fish sauce is added to all kinds of Thai food from soups to noodles. It is used to spice up an otherwise plain Jane dish. Usually in Thai restaurants, there is a bottle of fish sauce on every table to be applied as desired by each customer.
Thai restaurants don’t even offer soy sauce as a condiment. I live in Thailand and eat at the local restaurants almost daily, and none of them have soy sauce available.
In the grocery stores here in Thailand, soy sauce is stocked but it is not prominent and you can tell that it is not a big seller. However, fish sauce, hot peppers, and many other spices are in demand.
Usually, soy sauce is only offered in Thailand when eating sushi. I have a bottle of Kikkoman soy sauce in my refrigerator and the only time I use it is for sushi, actually.
So if you are allergic to soy or just don’t like the taste, you don’t generally need to worry about it being in Thai food.