I can also second the recommendation on Hua Hin,
we have gone twice this year - 1st time Hilton and 2nd Hyatt - both times to play golf - there are 5 fantastic courses - all different and very challenging.
We aranged all transportation through a Golf Tour operator - from pick up in BKK and back - including tee times every day and the tarnsportation to the courses. Hotels we arranged ourself.
Can also second the piers for Seafood in the harbour - went there every night.
Cheers
Thomas