Hi, Jack.
In English, if you say that "can I have a cup of tea?", it is less polite than: "can I have a cup of tea, please". Right?
so in Chinese, if you want to ask politely,
you say "我可以要一杯茶吗?(wo ke yi yao yi bei cha ma?)"
it is the same with "can I have a cup of tea please"。
here "可以要....吗(ke yi yao....ma)" is a polite. if you are rude you don't ask, and just say "我要一杯茶!(wo yao yi bei cha!)"
and what I want to say, there is a lot of ways to say that in Chinese also. for example: “给我来杯茶(gei wo lai bei cha)”,“拿杯茶来(na bei cha lai)”... those are a little rudely, like command others.
if someone asks you a question, such as "would like something to drink?"
you response "yes,please".
it is the same with "好的,来点吧(hao de, lai dian ba)".
it doesn't thanks but means "ok, give me a little" ...
do you understand? hope it helps ^^