You could save yourself a lot of $ by doing any of the following:

1. going to a place that you can travel to by road instead of flying - Hua Hin -ChaAm-Pranburi, Pattaya-Jomtien or Rayong -Ban Phe areas.
You can get a car or taxi down to Pattaya for about 1200baht (maybe cheaper ... depends how well you bargain) and organise another one down there to take you back to Bangkok. Or do the deal for the round trip. Hua Hin-ChaAm area would cost 2000-2500 baht I think.
In all these places there are places where you can sit by the pool or on the beach with a drink - in Pattaya-Jomtien try Rabbit Resort (very nice) with its own private stretch of beach with food and drink service, Cabbages and Condoms - beachfront location but up flights of stairs, lovely grounds, seaview, lovely rooms.
In Rayong, there's Rayong Resort - lovelybeachfront resort, but not near town so you need to always get taxis to and from. There's also Novotel Ban Phe Rim a few kms out of town - several little bars outside on the road and also bars on the beach just outside the hotel.
Ditto for Palmeraie (spelling??) - this is older and quite far from anything, but a great place to chill out for a few days.

2. using a budget airline - that puts Samui out of the equation as Bangkok Airways has a monopoly with Samui flights, but you could fly out of Bangkok to somewhere else in Thailand or nearby countries - check the budget airlines websites.

3. getting a package deal out of Bangkok to beach resorts. These packages include airfares, transfers and a couple of nights accomm (variety of hotels to choose from) and you can extend the stay by paying for extra nights. We took a 2 or 3 night to Phuket a couple of years ago (Thai Airways) and added extra nights. It was a terrific deal.

4. you could also investigate Malaysia - some really nice beach resorts at Kota Kinabulu and smaller islands off the east coast. Airasia has cheap flights out of KL to these places.