In Thailand, everybody gets a basic education in English, so they all theoretically understand atleast a little bit. In my experience, Thais are excited about learning the English language, and love practicing on you, assuming they can work up the courage. This is especially the case with the younger generations.
For example, while shopping at a Floating Market, we were stopped several times by students wanting to ask us questions in English (probably for a class assignment).
Just as they are excited about learning English, they also LOVE when a “farang” tries to learn/speak Thai. You’ll catch more flies with honey than vinegar, and you’ll get much farther in all situations with terrible Thai rather than impeccable English.