Thanx and thank you

Everyone knows about thanx and thank you right? It is very common for anyone to say it to anyone. 
However, the weird thing about some people in the world is that it can be very hard for them to spoke those words towards a certain kind of people. (Those people i am talking about are customers, some of them not all) 

I know the term 'customer' is a very board term. 
So, lets break it up into a few categories:

1) polite customer 
These are the type of customers at are polite to you, who is the server. They would say 'excuse me'; 'may i'. They would also smile at you and most importantly, they would say 'thank you' in the most appropriated way. This are the customer who would receive the best services and definitely a cheerful and polite server. (because if you want people to treat you a certain way, you treat them the way back) 

2) busy customer/impatient customer
These are the customer who would came, looking in a rush, choose their stuff very quickly, make a fast payment, said thanx, grab their stuff and went off. This is the normal busy customer. But there are always these other kind of busy customers. For example, when you are busy with your work, there would be this customer calling out in a very hurried tone, making you believe that that person is in a rush. When you are ready to serve the customer, he/she would take their time picking what they want in front of you. After that, once you pack their items, then they would find the amount that they need to pay for the item. (if you are this kind of customer, please dont expect a smiley service. Unless, the server is required to do so.) 

3) ignored customer 
I am not talking about customer who are being ignored by the server and would walk off feeling horrible, but more towards customer who would ignore the server. This kind of customer would be that when someone approaches them, asking 'may i help you?', they would just keep looking at what they are looking and just pretend that no one is there. Or, there are chances that the customer would walk to the store with earphones on (clearly showing that they dont want services). 

4) picky customer 
There are customer who wants their items to be perfectly perfect. Like when you are selling products (merchandise) they would want it to be new, just took out from the packaging. Or, if you are selling food, they would want it to be freshly make today (cases are very common when you are working in f&b retail.) 

So, thats it. These are some of my personal experiences that i encounter during work. Also, i realise that by saying thank you, really can makes the server's working time better. Appreciate their help by saying thanx or thank you. 

Here's a bonus: 
* road asker
Some of the potential customer are actually a road asker. They will appear out of no where even when they know that you are busing (especially when you are dealing with one of your customer). Since the store that i am working at is a u-shape corner shop, passer-bys have the tendency to just dropping by the store and ask for direction. I understand that you are unable to find your way so you are asking for direction. However, after you got your answer, it is polite to say at least a thank you or thanx. But no. Some of them would just walk away like nothing ever happen. It is something that is really rude, it makes the person who replies you feels that he/she is being played by you. So, at least says a thank you when someone tells you the answer for your question, even if it is not the answer that you are looking for.