The problem of shyness in Thailand

I have been living all over thailand for 4 years now, and at first i really thaught the Thai shyness was very cute and charming. However the longer i stay here the more i see it gets in the way of things.

Example; yesterday i went to 7/11 and i ordered a hot coffee in thai, the girl that was taking my order seemed to have some kind of programming malfunction as she had no idea what i was saying. After repeating my order in thai 3x very politely i ended up with a.... cold coffee (kafee yen)

I told her i ordered a hot coffee and again i got met by a awkward smile and what seemed to be fear in her eyes for this white guy that was talking thai, eventually her co worker stepped in and scolded her in thai saying: he told you in Thai, what is your problem!

This is one of many examples and i really want to know why this is so prevelant in thailand.