So I've got a long layover in Bangkok on my way from Delhi to Perth. I asked on the Lonely Planet message board for suggestions as to what I should do in such a short time. The following is a collection of the answers I received, which I put here to make it easier for myself to read and refer to them again later. Travel in the age of the internet: it's a wonderful thing!
For the easy way, grab a taxi out the front of the airport and ask to go to the Sukkhumvit area. This is downtown city and has shopping and eating. For sightseeing, grab a cab to the Grand Palace and you can spend a couple of hours looking around. Or go down to Chinatown and the waterfront area. Or take a short river cruise. If you've got limited time, the cabs are fairly cheap and fairly reliable. Most know where they're going. Just insist the cabs use their meters. It should take about 20 to 30 mins(depending on traffic) to get into town. Fare, including tolls, is about 350 TB. Just give yourself plenty of time to get back to the airport in the afternoon traffic.
The airport is about 20 minutes by taxi from the big hotels on the river. Its about $4. You'll want to see the Grand Palace and Wat Po. You can get a water taxi or sightseeing boat at the landing near the Grand Palace. A tuk-tuk can be a fun way to see the town as well. You should have time to enjoy these sights, maybe a bit of shopping, and lunch. The patio cafe at the Shangrila Hotel is a good spot. Have fun.
you could grab a taxi, go to the charming ko san rd, purchase yourself a fake student, and journalist card, and save yourself some money for future occasions.
:-)
I'm pretty sure that TAT operates a day tour service for people on stop-overs like yourself from Don Muang airport. Don't have the details handy but your travel agent should do (if someone here doesn't). The tour enables you to get around some of the immigration hassles (such as the 500 baht departure tax), I'd recommend it if its your first time in town.
Check these:
http://www.atta.or.th/forvisitors/bangkok_transit.htm
just dump your guide and arrange a pickup time. You will have to go the the gem shop but thats ok and painless. Fast-track in & out of immigration and very good value if there are 2 of you
Pics and Info on Siem Reap, Angkor & Vietnam
Beware the tree snakes ;->
Yo...go get an authentic Thai massage...will help w/both jet lag and a sore bum from your flight. It'll relax you too, and you'll sleep like a baby on your flight to Perth. Check the LP for reputable places.