Some of the people I know call me simply "papa" without a name.

Most of hem are only a few years younger than me.

Some others, mostly good friends, call me "brother".

Again without a name.

Most of these people are also a few years younger than me.

What is the meaning of this title calling?

In the Thai language it is commonplace (and friendly/affectionate) to call people by familial titles according to their age relative to yours. So everyone is brother/sister, aunt/uncle. mother/father. grandmother/grandpa etc. (Actually in Thai it is further refined as there are different terms for older or younger sibling and for aunt/uncle older or younger than your parent). Status also weighs in and adds to "age". So a person of significantly more status than yourself may be bumped up a bit in title as if they were older than they are. And the converse, hence calling waiters "nong" ("little brother/sister") regardless of their age.

Not only in Thailand. This addressing everyone as a family member is the custom in most of East and Southeast Asia.

So they are simply expressing themselves in English as they would in Thai.

It is as mentioned an indication of friendliness and affection. And that you get "papa" when age-wise you might be more of an older borther/uncle, suggests either respect or that they take you for older than you are!

And that you get "papa" when age-wise you might be more of an older borther/uncle, suggests either respect or that they take you for older than you are!

Actually, some of the people who call me "papa" are significantly older than me and they know my age.

That's what confuses me.