Long week-end are great, except that in Thailand you are so close to the island and yet so far ! As transport eats up all your time to get there... Here is a preparation work I had done a couple of years ago when I wasn't yet sure where we could go to. So which island in Thailand can be reached on a long week-end (or week-end) !?
I compare in the file: Koh Lipe, Koh Samed, Koh Samui, Phuket and Krabi
When I prepared this comparison - we went to Koh Samed for this particular long week-end the file was for. We didn't chose the right beach and the right hotel, plus the dive school I could find was actually closed. ( Now I know why they didn't answer my emails / call... ). We stayed at the Lima coco resort and it was again another horrible rip off for tourist. Very bad value for money and the food was horrible. We ended up eating at the neighboring resort. Since then I have avoided Koh Samed, but friends from Bangkok have been to other beach and had much better experience than mine - so better you look elsewhere for another testimony or go to make your own opinion.
If you are still into super backpack mode, you could go overnight from Khao san road to Koh Tao and fly back from Chumphon... could be done (quite expensive though for a week-end) - but my "aging" bones can't sustain long overnight bus rides for just a week-end anymore...
You can check my detailed post on how to get to Koh Lipe and dive there for more in-depth costs & how to. Overall on a long week-end, it's not worth it - you can get the super early flight that makes you arrive at 7am and then pay a private taxi to Pak Bara and catch the 8am-ish ferry to Koh Lipe to be on the island by 10 am. But the truth is, the ferry will stop at these "photo" spot on the way and it's quite annoying - and you would spend quite little time for the money spend to get there quickly back/forth and the fact that you will have a whole full day return trip. It's only worth it if you have 5 days (2 days transport and 3 days on site).
See above - we didn't particularly like our experience there ourselves so we never went back. Koh Samed also practice a dual tariff for the entrance fee. A whopping 500 THB (if memory serves me right) for foreigners, and no matter if you have work permit or not - it's all about your face. This further convinced us that for not such a great place - and the price - we were not going back.
Well since this island is very well trodden with loads of transport. It's actually a very good option for a long week-end. Just hope that you can get an affordable flight with Bangkok airways...
Loads of affordable flights to get there - if you pick a beach in the north which are less touristy - Phuket is a nice place to stay ! It has all the 5 star resorts and activities to get busy. If you want to make it even more affordable: rent a car from the airport. The taxi mafia there is well organized and even metered taxi charge the same. The ride to/from the airport can cost you as much as your flight from Bangkok and is equivalent to 2 days of car rental... So if you intend to move during the week-end: rent a car.
If you have a long week-end and are diving: The southern route of the diving cruise MV Giamani leaves on Friday night and comes back on Sunday night from Chalong. Then you can rest on Monday and take a flight back to Bangkok in the evening. They do all the famous dive sites around Koh Lanta and Koh Phi Phi !
We have done this route twice and we love it ! More tips about diving in Thailand ? Check this post out !
This is probably one of the easiest as well. From Krabi airport you can hop of one of those cheap bus to Ao Nang beach and in one hour you can be at your hotel resting. Pick a resort to get lazy and don't do much. I wrote a dedicated post on a week-end in Krabi with some nice hotels recommendations and activities to do.
A little further than Pattaya - and really less touristy. It's where I had my best seafood in Thailand EVER ! Along Laem Mae Phim Beach . But this beach (albeit very nice) is not great for swimming if you like some privacy as its packed with thais on week-end! We do prefer the smaller Coca Cola beach - which has it's own small chalet you can rent and a super simple restaurant. Most nice resorts are located around the Novotel Rayong and it's where the big and long white sandy beach is.
Hua Hin / Pattaya:
These are just excellent and easy week-end - from 2 to 3 hours drive from Bangkok. Mind the traffic on the first week-end of payday. Hua Hin is more laid back and family oriented whereas Pattaya and his sulfuric reputation is where party goers would venture for less than official entertainment... South of Pattaya has family friendly and good accommodations - Jomtien Beach is also more family oriented.
There are so much more islands in Thailand which are gorgeous but on a week-end or long week-end are hardly accessible & worth the time / money.
You can check out Koh Mak for longer holidays.