If you are looking for good authentic style thai these are my current reccomendations:
Thai Grill - Valley (Currently undergoing a remodel but should open back soon)
Thai on First - Downtown (they have strange hours and it's not unusual to find them closed at 730PM on a Thursday night so call ahead)
Sala Thai - Airway Heights
Places that are average
Phontip Thai - North
A taste of Thai - North
Bangkok Thai (Riverwalk location only)
Places to Avoid
Thai Bamboo (They went bollywood a few years ago and the food is equal to Chinese mall food)
Bangkok Thai (South Hill location - don't know why they suck but they do)
Linnie's Thai (Locals brag about it, been here the longest but it's pretty pathetic)
Linnies Thai II (Worse than Linnies Thai)
Good luck and report back which places you like the best.
if the Thai Kitchen on Pines Rd in the Spokane Valley is still open, i think the trip from downtown Spokane would be worth it.
i never did care for Thai Bamboo, but that was over 10 years ago.