In preparation for my trip, I downloaded the World Nomad's Thai Phrases app.
It comes with six categories: Numbers, Introductions, Directions & Transport, Places to Stay, Travel Safety, and Dates.
I like how it says the phrases, since Thai is a tonal language. They are limited, with only five or six per category usually, but seem to cover the basics. For example,
Excuse me: Kor toht
Thank you: Korp khun
It's the basic phrases under "Travel Safety" that give me pause: