I have been able to find out some information from a website (in Thai) which confirms the dates given above, and also has some of the artists who will be appearing listed, as follows;
International artists
+ Ben Besiakov Trio
+ Ibrahim Electric feat. Michael Blake
+ Mikkel Nordso Band
+ Malene Mortensen feat. Jonas Johansen
+ Bill Bruford
+ Lazaro Valdes from Cuba
and Thai artists
+ Crescendo
+ Lipta vs. Radklao Amaradit
+ Doobadoo
+ T-Bone
It also says there will be 2 beach stages again (presumably by the Hilton and Sofitel as it was 2 years ago) and a 'Jazz Alley' between the 2 stages with small stalls and shops offering a variety of things such as hair braiding, OTOP etc. Heineken are again the sponsors and have said that as well as the usual beer stalls they are setting up a 'Charity Zone' with some proceeds going to the Thai Red Cross, where for a payment of 500 baht you can sit in this exclusive area (near the Sofitel stage I believe)
and get free beer all the time (my bold lettering...

)
From another website I have also garnered the following, which will be of interest to jazz enthusiasts
Ace alto sax player Kenny Garrett’s agent tells our correspondent that KG has been booked for the 2008 Hua Hin Jazz Festival, joining Mike Stern and Dave Weckl who we reported earlier were also booked.
However on further investigation this is unlikely as the latter 2 are apparently booked for the Harmony Festival in California the same weekend, but are also booked to play in Bangkok on 14th June; festivals are notorious for last minute changes though so you never know. Ted Kurland Associates are the agents for Garrett and have him on their website playing the HH Jazz Festival on 13th June (presumably before the date was fixed), so that is at least a possibility and would be a major coup if it happens, and worth the admission price (

) alone!