My Thai friend said that she normally uses this word คุณ for her boss. But for other people it is usually พี่ , น้อง , เธอ or their name.

When you hear Thai people speaking to each other and they are peers, do they ever refer to each other as คุณ? How common is it?

คุณ is a title of respect, so wouldn't normally be used amongst equals, only with people of higher rank or status.

Compare it with Mr. or Mrs. in English. These days you wouldn't normally say "Good morning, Mr. Smith" to a colleague when you arrive at work - it's too formal. However, you probably would if you were greeting the company chairman (assuming, of course, he's a man and his name is Smith).

Favorite use of คุณ:

Edited May 7, 201511 yr by DavidHouston

I was once criticized that my nickname would be braggy

"Khun" being another transcription sounding like khoon [note to our English friends].

http://www.thai-language.com/mp3/E131135.mp3

Edited May 7, 201511 yr by KhunBENQ

If you want to hail someone whose name you do not know, say "khap khun". This is the equivalent of "sir" or "madam" in English.

Peers who are in the least familiar with each other will not normally use the pronoun "khun" amongst one another. Khun is used in more formal social situations such as dealing with bureaucrats. Khun is also used when you are not familiar with the other person, especially in regards to age and social status, the two main stratifying lines of Thai society. When in doubt use khun. If the person is clearly a generation older than yourself then lighten up the formality by addressing the person as either "khun lung" (uncle) or "khun naa" (aunt). But when people are two generations older it does become more common to hear Thais addressing the elderly as "khun yai" (grandma) or khun taa (grandpa) to show respect for age. Note that when addressing such elders, use the pronouns for the mother's side of the family.

If you want to hail someone whose name you do not know, say "khap khun". This is the equivalent of "sir" or "madam" in English.

You mean khun khap.