Thailand forum

The best spot for short weekenders from Bangkok is Ko Samet -- I'd start with that and then try further afield. The Ko Chang group aren't too bad, but just going for a weekend is rushed. Further afield you can always fly south to Samui of Krabi, but again for a weekend is tight.

for a single female pattaya is not the place to go, unless she's a lesbian looking for bargirls.

samet or hua hin is ok alone for beaches. otherwise fly south.

I'd agree that Samet is the obvious start - followed by the Chang island group over near Trat. I also agree that Pattaya is not such a good idea.
Islands further afield are okay if you can afford to fly. You can reach a lot of the Andaman islands thru Phuket, Krabi or Trang (I don't think the flights to Ranong for Ko Phayam and little Ko Chang Andaman side coincide with weekends - check Air Asia). And you can fly onto Samui for the southern Gulf islands - note that the weather tends to be a fair bit wetter there between now and late Dec, early Jan.
Overnight train trips will get you to Trang for a whole bunch of nice islands and to Surathani for Samui etc - I'm not sure of the return trips' timing: whether you can get an overnight sleeper back to Bangkok. But you can get overnight bus trips to/from all the southern areas - mind you my bus from Ranong got into Phuket at 4am which means you are going to be yawning a lot at work on Monday.
A good site to check for overnight bus/fast Catamaran trips to Tao/Phangan/Samui is Lomprayah - this outfit is often praised and seems not to be dodgy like a lot of the non-government-bus operations out of Bangkok. Tao and Phangan are great starter islands out of their wet season.

hi definitely samet for the weekend only a few hours by bus and you dont seem to get the excess of drunken western tourists as much as you do on other islands

jep bungalows are a good place to stay 350 baht i think for shared shower and toilets but you get a lovely big bed clothes rail and tv with movie channels definitely good for when it rains ;)