Leaving out the word Ao makes no difference to the meaning.
[QUOTE=EihTooms;2222860]Yes, in terms of basic communication there might not be much technical difference between "Mai Ao" (I rarely hear farangs add the "Khrap" or "Khrup" to it), which essentially means "I don't want it" and "Mai khrup, karp khun khrup", which essentially means "No (politely) thank you (politiely)". [/QUOTE]I don't fully agree. A dictionary will tell you that Mai is an adjective or adverb if you know anything about Grammar. So Mai really means "not. ". There is no Thai word precisely the same as English Yes or No, since English No can mean several different things. No I don't want it, No don't do it, No I don't agree, No I don't like it, We have No bananas, there is no place better, etc. , even can be used by some regardless if they agree or disagree since they never ever say Yes to anything. LOL Even in English you can see that No is a short form of "Not want", "not agree", "Not like", "not have", "not any".
So "Mai Khrap " has left out the verb and implicitly means "not want", "not agree", "not have" etc. I. e. "Mai ao", "Mai hen duay", "Mai Chai", "Mai mee". "ao" is a very informal word, so "mai tong gaan" is slightly more proper. Adding "thanks very much" at the end is like saying thanks for the help anyway unless interpreted as sarcastic. Thais normally answer "Mai Khrap" in my experience when they are asked a question including a verb so that same verb would be understood in the answer. Would you take this? Answer "not (take) thanks". So I don't believe I hear it very often. More normal is to include the desired verb, where in English we don't.
Perhaps "Mai Khrap" can be interpreted as "Mai Tong Gaan Khrap" (I don't need it) which may seem softer than "Mai ao khrap" to some. Ao is a very common word though, so not a big problem to use it. Girl "ao mai" (do you want (me)). Answer "Ao si. rew rew" (yes absolutely and urgently)! Thais like euphemisms. The girl won't usually ask "do you want to fuck me?" "yet chan mai" It is a bit too direct and rather profane. Maybe she could be naughty and ask "boom boom mai"
You can check with a Thai Language teacher, if they agree with my views. I did study Thai for years, but don't have a teacher for recent years.
Perhaps I will ask my teacher, the implication of using polite "Khrap" too much to inferiors. I am not clear if Thais will think we are just extra polite, or perhaps not understanding Thai custom if too polite to people younger than ourselves and not in a position of official authority. I don't see my GF being too polite to young sales persons. I think she uses "Kha" sparingly. Obviously extra polite to monks and older people in the community though.
"ja" maybe a good alternative to "khrap" to be more polite but less formal. Maybe requires Thai skill to use correctly though.
I remember one Farang hearing "khorp Jai" from his Thai Mrs. a lot, then used it with a monk, which was a big mistake (rather impolite). Should be used to those of inferior status only, or sarcastically when "thanks" but not meaning it, like Thanks but I did not want it. So I only ever use "Khorp jai" when reluctantly taking or receiving something.
Yes it is better to err on the side of being too polite. Therefore as Farangs, it does not matter too much if we add "Khrap" a bit more than we need to.
To salespersons I try to use the Thai equivalent of I am just looking so far "Khae duu chery chery khrap". I don't think think sales persons in department store are really aggressive compared to some bargirls. LOL Street sellers, maybe, but I just refuse to talk to them at all. I don't feel compelled to waste my talking to every person on the street that accosts me. If a tourist needing directions to somewhere that is different.