Hello Turkish,
If flying eats away at the burget too much: a few years ago I took a night train with sleeper from BKK to CM. I found it pretty comfortable and cheap (especially because you save a night of accomodation). Open the curtain in the morning for some nice views.
Try to get your ticket a few days in advance. I believe around 300B should get you to CM. Look up Lonely Planet for more info if you're interested.
Cheers,
Maarten