I love this place for its authenticity and unpretentiousness. Their Khao Soi is out of this world. IMHO, even better than Salad King's Khao Soi. Every time I'm in the area and happen to crave authentic Thai food, I go to Thai On Yonge. There are too many inauthentic Thai restaurants in Toronto. This place is a little gem in the heart of Toronto. It's usually empty, which results in fast service, but don't let the absence of patrons fool you. Their food tastes great. I recommend their Street Pad Thai. It's well worth every dollar.
In terms of prices, everything on their menu is reasonably priced. Your bill won't break the bank, while the food will leave your tummy happy :)