The nearest resorts are Jomtien and Pattaya, Pattaya has an unsavoury reputation but I believe there are some nice parts to the town with good hotels and beaches. Another resort within easy reach is Rayon though I don't know anything about this resort.
Two other resorts within easy reach of Bangkok are Cha Am and Hua Hin I have stayed at both resorts, I preferred Hua Hin as there was more to do, with shops and restaurants. The beach there is not brilliant though but all the hotels have lovely pools. It's 12 years since I stayed in Cha Am so it's probably changed quite a lot since then. All of these resorts can be reached by taxi within a few hours. It takes about three hours to get to Hua Hin, less to the other resorts. I have only ever been to Thailand in winter, it's probably hot and sticky in August with a fair amount of rain but perhaps you can get more info. re the weather from another poster.

Judith

Your right some parts of Pattaya can be unsavoury but Everything is available in Pattaya, its a good reasonably priced base to do trips from, there are dozens of tour companies and although you have to shop around you can find plenty to do from there.

If you dont like the "unsavoury parts" then you dont have to go there, I come here for 6 months of the year through the winter and beyond and have been just about everywhere traveling by sea/train/car/bike/plane, and I dont have to go anywhere I dont want to here and I stay in an area where there are a few bars but is relatively quiet, a great Guesthouse, you can google Canterbury Tales Cafe Pattaya, there is free wifi, dvd player & free dvd's, electic safe, 24 hour security, very well maintained guesthouse and they have a website booking facility.
The Cafe/Restaurant serves all day English breakfast and there is a huge bookshop incorperated in the cafe so a great atmos.

So dont let Pattaya's snubbers put you off, there is a complete fascination here and I cant imagine traveling anywhere else for my long term holidays.

we went to hua hin 2 1/2hrs by local bus from bangkok for us it has everything give jings guesthouse a try great rooms staff etc

I would second Hua Hin / Cha Am region as well, certainly compared to Pattaya.

Plenty of hotels for all budgets. I've stayed in the Holiday Inn (when it was the Regent), Putahracsa, and Aleenta, and seen the Evason's. I'd make a recommendation, but depends on budget and the type of person you are?