Most of the sois play hip hop but don't expect anything cutting edge and expect it to be mixed up with all sorts of other music (Thai, Rock etc..)
Soi Crocodile is more Housey based, which in my opinion makes it the best Soi for music, but that's just my preference.
The clubs all play some hip hop, Tiger has it's hip hip hours around midnight and 2am I think. Baya Beach seems to always have good music whether it's hip hop or Housey stuff. Banana likewise.
Just don't expect it to be that great, good music is one thing sorely missing from most of the bars/sois.