Not sure what you mean by a "sponsored ride". Usually there is an angle, such as record fast time, or huge distance, bangkok to Hua Hin isn't really spectacular as far as getting sponsored. It would be a good ride, possibly I am misunderstanding what you mean. Is it a one day trip or a few days?
Last year I rode from Luan Prabang to Surin, back up to Nongkhai(different route), then Loie and finally Udon. This year I rode from Khon kaen to Lop Buri, ayutthaya, Korat, and then zig zagged all over southern Isaan. I love cycling here.
If you go to Crazyguyonabike.com you can find tons of useful info. If you do a search for Hua hin at that site you will find journals with detailed info about the route. If your bored you can type my name in the search window "marcus byizy" and see my journals.
Cycling in thailand is great. I have encountered way less road rage and stupid drivers here than in Canada. My biggest tip would be get a wide mouth water bottle, then you can just top up with ice in every town.
If your in Bangkok try getting ahold of the Thai cycling association, they are a great bunch and do a lot of good group rides.
Good luck with your trip and I hope you post the details and some pics when your done. If you have any questions about gear or anything feel free to PM me.