Thailand trip in January
 

I will be taking my 20 y.o. son on a 2-wk trip to Bangkok, Chiang Mai, and Angkor Wat in Jan. Thanks to all for the wonderful, useful information on this site. I have a few questions and would appreciate any advice:
Is it better to take a cab from BKK (arrive at midnight) to our hotel (Marriott Resort and Spa), or arrange transportation in advance?
We want to take a trip to Ayutthaya from Bangkok one day-should we arrange in advance or just arrange through hotel once we arrive (will only be in Bangkok 4 days)?
Should I bring any Cambodia money for Angkor Wat, or will I only need U.S. dollars?
Thank you!

Taking a cab from the airport is quick and easy. You can arrange transport in advance, but it will cost you significantly more.

Arrange your trip to Ayutthaya once you get to Bangkok.

You can't get Cambodian money except in Cambodia, as it's worthless outside the country. Actually, it's close to worthless inside the country. Everyone wants US dollars. Take lots of small denomination bills. I went to my bank and got a 100 1 dollars bills - new - plus $5s and $10s for larger purchases. You will get some change in riel. I gave away all my riel to amputees, to the shrines, etc.

Taxis are available 24/7 but if you want more comfort just go to the Limo counter after baggage reclaim and they speedily whisk you to a nice large sedan, can be a Merc/Volvo or large Toyota, doesn't cost that much more than a taxi but it's fine service and nice comfort. No need to book the limo in advance, open 24/7 easy. As kathie says arrange local trips once in BKK so you can decide there and then what you want to do, you might change your mind, you can book easily with hotel travel desk.

Kathie,
You seem to be a well travelled woman.Therefore I'd like your opinion on the Conrad Hotel,Bangkok.
We got a bargain rate for their Executive Floor - we're going in January for 9nts.
And what do you suggest as a "must see" in terms of sightseeing - can you do the Bridge on the River Kwai in a day ?.

You can do the River Kwai in one very long day.

i would arrange with aac limo to take you in advance....or have the marriott get you....it is overwhelming after a long flight to deal with it all the first time in bkk...marriott charges about $36....aac about 1/2 that