Of course, am not putting in general that all thais are good nor all thais are bad. I just had one experience in MBK wherein I asked discounts, then the saleslady shouted at me and said "Go away!". I felt embarrassed but I've got nothing to do or say. I also experienced that when a Thai does not understand your english, the easily got irritated.
Please share if you know some Thai traits whether it's good or bad.