Thailand is famously known as the Land of Smiles, and its residents pride themselves on being gracious and accommodating. As a collective culture, Thai people are taught to be more concerned with what’s best for the group rather than what suits them personally. Perhaps this is why “no” is always tempered with a “yes”. “Not yes” seems to imply in one small phrase their regret at not being able to consent to what you’ve asked. In fact, when mai chai is proffered, it’s often with downcast eyes and a small bow called a wai or a hand waved in front of the face apologetically.
http://www.bbc.com/travel/story/20170123-where-people-dont-like-to-say-no
