Salad King is what I would consider to be cheap and cheerful Thai - if your idea of cheap and cheerful involves a noisy packed room of people waiting for tasty (if not authentic) food.
Service is very quick and you're never waiting long for food. I would say the food is consistently good (although the spiciness varies, despite ordering the same number of 'chili peppers' each time I'm there). Favourites include the spring rolls, wonton soup, basil beef, phad thai, and green curry.
Yes, I understand that there are way more authentic Thai restaurants in the city. But if you're looking for a fairly inexpensive meal close to downtown where service is prompt and the food is pretty good, Salad King is a good choice.