bangkok
It depends on what you want. Bangkok is a huge city. If you want to be by the airport, try the Miracle Hotel Airport. It would not be my first choice for staying in Bangkok because it is by the airport, but for a quick overnight stay with a shuttle to the airport it is fine. Go to one of the discount hotel sites to book it. I think Agoda.com offers some of the cheapest rates for thailand hotels. If you want to stay downtown (I would recommend) the Hilton Millenium or several of the hotels on the river. I like the hilton because it is on the far side of the river and they have a river ferry boat (free) to the BTS which is the over head train. The BTS is relatively new and better than most of the mass transit systems in the usa. The only draw back is that it doesnt cover enough of Bangkok. A new airport stop has recently opened on the metro but I am not familiar enough with it to tell you about it.
If you have money to spend, stay at the JW Marriott, rated as one of the best hotels in the far east. Radisson has a very convenient hotel downtown too. It is within walking distance of the Siam Center and the hotel is very nice. It is the Park Plaza Sukhumvit hotel. You can book it on the radisson site. It is extremely convenient to the bts and to shopping. The Hard Rock is just down the street a few blocks. Radisson has a new Radisson Blu there too but i have not stayed there. For sheer convenience and a very nice hotel i would choose the Park Plaza Sukhumvit or the hilton. BTW the way to get around Bangkok cheaply is to use the BTS OR use the river boats. I am not talking about the tourist boats! You can ride up and down the river on the public boats for something like 20 baht-that's less than a dollar. If you have questions, you can PM me. I have been to Bangkok 3 times in the last 18 months. Incidently, while the airline Deals (?) are better than booking separately at rack rates, you can do much better on your own if you know which sites to go to. Also you get no deals of consequence if you are on an award ticket.
In thinking about this, you should also go to flyertalk and go to the travel tab and go down to Thailand and read about how to deal with the taxi drivers and the Tuk Tuk drivers. Also learn a few words of thai because they dont all know english- you should at least be able to get to the bathroom. Forget about trying to read thai- just learn to speak it. A few phrases have served me very well. Finally book a trip to the Tiger Temple (do not use the hotel for that since it will cost 2 or 3 times as much). I have an earlier post on this in this forum.