While a smile will get you far, as a foreigner in Bangladesh, learning a few phrases of Bangla is a good idea. I am not a linguist so I’ve made up my own system of phonetics. These are some of the phrases I have learned:
PAH-nee — water — This is the Bangla word I used most in this hot, hot, hot land.
DON-ah-bawd — thank you (foreigners like to use this but I’m told it’s not really part of the culture. I’ve seen nods of the head or a closed fist to the chest used as “thank you” and that works too).
Sah-ley-al-eh-kyum — greetings (it’s from Arabic and is how you greet people or announce your presence) — I often just say “good evening/good day/hello” and that seems to work.
DECK-A-hawb-aa — see you later.
AH-che — gotcha or yes, I’m listening to you and I understand that you are speaking. I like “gotcha” because it rhymes with the Bangla word.
EK-tah — one of (EK is one).
SHESH — done as in “enough” and “it’s over.”
LAWG-bey-nah — No need or I do not need it (useful when rickshaws try to run you over in their eagerness for your custom). This is the phrase I have found most useful.