This is a really late reply but I just had to explain haha. When a man is speaking, "Phom" is far more polite than "chan", and he uses it to generally address a woman who is basically his equal. If he were to say "chan", it can sometimes be to a maid for example, or someone he may consider less than him. A lot of the raeng lakorns have a male address the woman this way - such as Sawan Biang - but this changes later on in the drama. Btw, I say this speaking in general (it doesn't always make the guy worse or anything if he says "chan").
Khun is formal, but also addressed to people you respect. It is the safest word for 'you' if you're a foreigner, and husbands and wives sometimes address each other this way as well. If a man says "Khun" to a woman, he also refers to himself as "Phom"
But if it's a casual or close relationship, the name being used for "I" is the best way, and even though it's not exactly formal, it is really polite. You may say your name for someone who is older than you for example, or to your bf/gf.
I hope that clarified for you