I am going to start this post off with a strong opinion - Pusadee's Garden is the best Asian restaurant in Pittsburgh.
The patio garden, expansive menu, service, and food quality all stand out as exceptional. You don't need the frills of Umami or Plum to have a great Asian meal in Pittsburgh, and Pusadee's Garden proves that.
Pusadee's Garden is located on Butler Street in Lawrenceville. With over 50 Thai dishes to choose from, it is impossible to not find something that sounds delicious (unless you don't like Thai food... which like....you're wrong).
Even though the food is marvelous, it is the atmosphere that really sets Pusadee's Garden apart. The outdoor garden seating is an oasis, similar to what I assume dining in the Hanging Gardens of Babylon would be like. Because the bulk of the seating is outdoors, the summer is the time to go to Pusadee's Garden, especially on a nice day.
Additionally, the service is very fast - Pusadee's has it down to a science. While you may have to wait for a table, you will not wait long for your food to arrive.
Pusadee's Garden is BYOB, open for dinner every day and lunch on Saturday and Sunday. Pusadees is no Pittsburgh secret, so call ahead and make a reservation or be prepared to wait for a table.
The restaurant closes from December to March because, as mentioned above, the bulk of their seating is outdoors.