Living in Seattle for the past year, and loving Thai food, I noticed that there is a general overall difference in the type of restaurant a Thai place is between Reykjavík and Seattle.
Thai places in Seattle seem a lot fancier then in Reykjavík. In Seattle you most likely have to order a table, or at the very least have a waiter show you to your table. In Reykjavík, on the other hand, Thai places tend to range all over the place, all the way down to having only 4 bar-like seats by the window.
The menu is also way more diverse in Reykjavík. In Seattle, you can pretty much guess the entire menu before you walk into a Thai place. While in Reykjavík a Thai place might only have three types of pad thai on the menu, or only sell soup, or even sell have 3 or 4 pages of stuff on the menu, including non-thai cuisine.
Generally, I like the Thai places in Reykjavík better then in Seattle.