ผม vs. ฉน

[llz]

Newalaan is absolutely right about the use and signification of the end particles.
As for the pronouns, ฉัน can be used by both males and females, but females use it in most circumstances (except very formal ones when they use ดิฉัน - dichan), whereas it is more informal and intimate when used by men. I often heard gay queens and ladyboys using ดิฉัน as a joke.
Personally I sometimes use พี่ (phii, dropped/long tone) when speaking to younger people, which happens quite often ... Speaking among themselves, the boys will always use กู (koo) but it would be totally inappropriate to use it as a farang or as a boy speaking to a farang. Anyway pronouns are mostly omitted in informal conversation when the context is clear.
BTW there is no such word in thai language like ฉน, which would be pronounced as chon (rising/short tone). "I" is ฉัน -chan, formally rising/short tone and informally high/short tone.

[cdnmatt]

Personally I sometimes use พี่ (phii, dropped/long tone) when speaking to younger people

I'm assuming you get some smiles when saying that?

You say พี่ (phii) to reference older people, and say น้อง (naawng) to reference younger people. Just take a young guy out for dinner, and watch him yell out "phii!!!!" every time he needs something.

Never heard any guys use "ka" at the end of a sentence though, except when they were 100% ladyboys and proud of it. heh, I remember I screwed the "krap" and "ka" thing up at the beginning, as I thought it translated to "sir" and "madame". So when I went to 7/11 say, and it was a female clerk, I would say "khawp khun ka", and walk away with a smile thinking I was being polite. Later on I realized the "krap" and "ka" depends on your gender, not the gender of the person you're talking to.

And yes, sorry, I misspelt it. I meant ฉัน.