I think you won't like to stay in Thailand at all after 7 days in Hua Hin - it is a complete package holiday type of town with "fish & chips" and europeanised thai food
I passed it once on the way from very quiet western thailand (Kanchanaburi area and all the way to Myanmar border) to the marvlous south beaches and I had to kill several hours in Hua Hin. I would not like to stop there at all
If you like to have a beach - there are much better places within 1 hour flight from BGK.
If you want something quiet and culturally bigger - go a bit north of BKK - Autaya or other historic cities, direction to Chiang Mai (afterwards further north to Chang Rai and Laos eventually).
If you want quiet and nature after long flights - go west to Kanchanaburi area (3 hours by a local train from BGK Tonburi station).