Adding fish sauce is a great way to make your Thai food saltier, but it's a no-no if you're a vegetarian -- it really is made from fish. Instead, try using soy sauce. It's almost as salty-flavored, but it's not made from animal protein. Both are better for you than pure salt.
If you need to use a knife at a Thai food restaurant, the food simply isn't authentic. In true Thai cuisine the food is deliberately cut into bite-sized chunks (if not smaller) so that you can handle it with the standard knife and spoon or, in some instances, chopsticks.