As we all know, the 'น้อง' [Noong] is expected to pay respect to the superior 'พี่' [Pi] in greeting by the 'ไหว้' [Wai] first. Therefore a lot of Thais want to shake-hands with
people of western culture to express this circumstance. As we (western) people are also polite, we accept that.
But in the (western) culture things are slightly different. In our culture the superior 'พี่' [Pi] may offer his/her hand to be shaked or not. It is therefore inappropriate
for the 'น้อง' [Noong] to offer his/her hand for hand-shaking. If you feel to be a 'น้อง' [Noong], please wait whether the 'พี่' [Pi] offers his/her hand to be shaked or not !