bangkok to koh samui

Train & Ferry will work best it seems for you:

Relevant Linkage

Hope this is of help.

The train station will sell you 'joint ticket'. This will include everything to get you there. There is no need to worry. The aforementioned site will provide the information you need. You can also take a bus. The southern bus terminal will be able to hook you up. There are cheaper buses from Khao San, but some of the operators are prone to theft. Lomprayah is a good one, but they go to Koh Tao first ... then Koh Phangan ... then they reach Samui. It really isn't too hard at all.

the bus takes 12 hours and is a really bad road at night.

for an extra 30 bucks you can fly

Same question asked yesterday:

http://www.lonelyplanet.com/thorntree/thread.jspa?threadID=1645513&tstart=0

Yep, train much better. I took the bus and my ass....well it's forgiven me.

Ferry, if you can't get a ticket in bangkok then simply book at pier.

Even at the bus terminal they can sell a combo bus/ferry ticket to you.