Very sorry to hear about your accident and glad to hear the sea sand sun helped you regain your felxibility :)

I think Hua Hin will be a fantastic choice since you just got back from Phuket. It's less than 3 hours drive from BKK and if you can try to avoid the public holiday weekends, you will feel like you have the whole town to yourself. The local is friendly, food is amazing and living cost is cheaper than some other tourist places. Its quiet enough to relax by the beach but I must warn you the water is not as clear as what you experienced in Phuket. The beach is not dirty at all but it's just the nature of the water on the gulf of thailand which is not exactly as crytal clear as on the Andaman side. All in all, I think Hua Hin will meet your requirements.