Notice the kind of English Tsetan uses while talking to the author. How do you think he picked it up?

Tsetan spoke short sentences, direct and simple. His English is simple; vocabulary not rhetorical. Besides he called the author “sir” everywhere. He seems to pay much respect to the author. He apparently was a tourist guide, whaich means daily interactions with foreign tourists. That is where he must have picked up the language from. It is quiet possible that he had broken knowledge of other languages as well.