Bangkok Airways customer service is the worst I have come across. I had booked 2 tickets from Koh samui to Bangkok, and then got them canceled.
Its been over 4 months and they just wont refund the correct amount to me.
I have emailed them at least 6 times with no reply to any of them. I have called them up 4 times, where the promises are big and they admit that my refund amount should be credited to me. Robing people of their money is a habit of Bangkok Airways.
So be careful Bangkok Airways should be last option. And even if one has no other choice don't cancel or your money is gone.