I've tried the super cheap (i.e., the sketch place on the corner of Alakea and King St with the big $5 sign in the window) and the fancier Thai in Honolulu (Phuket Thai, Keo's) but I always come back to Bangkok Chef. While it's not oh-my-god I'm eating in Thailand authentic, it's good, satisfying, always the same, and very affordable.
Here's some pics from the last time I was there (Nu'uanu location)
|Tom yum - nice & sour|
|Pad see ew|
|Green chicken curry with sticky rice|
|thai tea and pandan flavored tapioca|
Multiple locations including Manoa, Nimitz and Nu'uanu