This place is a very tremendous 4.5/5.
Our server was super helpful with meal suggestions and how spicy we should get them. She was also really attentive and was quick to fill our waters as soon as it dipped below the halfway point. Khao San Road usually has a couple of servers on hand, all whom looked like they were taking care of their customers well. Khao San Road is one of the few places I actually voluntarily want to give 20% tip because of the super great service.
I have never had a better Pad Thai dish anywhere in Toronto that can match up to the one at Khao San Road (note: I haven't been to Pai yet but I hear their Pad Thai is also quite good). The Green Curry is less creamy compared to most of the places I've been to, is less sweet and it has more of the lime leaf taste. It was different but not necessarily my favourite taste palette for a green curry. I heavily recommend getting the Khao Soi, curry base with egg noodles, and the Thai Iced tea.
This restaurant is really busy most of the time and lineups usually start even before they open. Keep that in mind as you plan your trip. There are 5 two-person tables and a bar space if those are full. I believe they are relocating to a larger location in the near future (~March 2016) so it should be much easier to get a seat after the move. They also have a sister restaurant called Nana which will might be interesting to check out.