
Depending on where you live, the length of your flight to Bangkok is going to vary a little. However, one thing I know is, it will most certainly be LONG. A typical flight out of a major US city can take 18-23 hours (including a stop-over.) If you live on the west coast of the US, you are in the best situation. Thai Airways International (800-426-5204) has flights to Bangkok from LA (flight time: around 20 hours plus abount a 1 hour lay-over in Seoul Korea). The cost of this flight is around $1,350 during the holiday season (till Jan 15th) after Jan. 15 the price is around $1,150 (remember you can save even more by going through a travel agent). If you've never flown on Thai Airways, I'd recommend it. They have some tasty flight attendants, the service is awesome and who knows... I've heard of several guys picking up their flight attendants and hanging around Bangkok for a few days with them. It just doesn't get any better than that!
If you are leaving from the east coast (New York), you will head the other direction (east) and have a stop-over in Frankfurt or another large european hub city. From the mid-west (Chicago) you will head to Tokyo or Korea first, have a lay-over (3-5 hours) and then finally on to Bangkok. The only good thing about International flights is that the alcohol is free. Of course, it's not a great idea to drink a lot in the cabin environment. Figures, RIGHT!
A handy page for getting ahold of an airlines phone number & Web address (if they've got one) is the Airline Toll-Free Numbers & Websites index.
These days, most major airlines fly to asia and in particular Bangkok. If you want to take the comfortable route, you can always fly domestic to the west coast and then fly on Thai Airways direct to Bangkok. Otherwise, just pick your favorite airline and check it out. Some of the major playing from the US are NorthWest, Japan Airlines (JAL), Korean Airlines, Cathay Pacific, Delta and Canadian Airlines.
Fares can AND DO range wildly depending on what class you want to fly, how much advance notice you are giving, what airline you are using and what time of year you want to go. High-Season in Thailand is from November through April. Prices tend to be higher at this time of year. Yet, if you live in a cold climate, this is exactly when you want to go right! Bargains CAN be had and I'd advise you to search around a lot before making a final decission. I have flown to Bangkok for as little as $800 and as high as $1,200 round trip. There are just so many variables that go into getting a good deal. Of course, if you insist on flying anything but economy, you are going to pay THROUGH the NOSE (like we are talking major bucks here dude -- like maybe $3,000 - $4,000 round trip OR MORE!)
TIP: I'd suggest trying to get a hold of a ticket broaker/discounter in a major US city. You can sometimes get MAJOR deals getting tickets through these guys. Of course, you can't always make changes to your itinerary but hey! What do you want, everything? At least for the present, forget about these "on-line" reservation systems on the web. I have played extensively with these and the prices they come back with are seriously wanked! Maybe this type of service will improve in the future.
If you are REALLY on a budget then you can always check into the Air Courier Carriers that need document carriers to Bangkok. Most of these leave only from the east and west coasts (LA, San Francisco and New York) and not so much from the mid-west (like Chicago). Still, it's worth a look. Check out the following sites for Air Courier Companies that have web sites.
The Air Courier Association
Worldwide Courier Association
The International Association of Air Travel Couriers
IBC Pacific, Inc.

Please note that the above temperatures are for Bangkok. If you are going to the north, like Chiang Mai or Chiang Rai, the temperatures will be cooler (especially at night and early in the morning). They can be up to 10 degrees cooler at these times. Also note that things seem to be changing temperature-wise in that it just doesn't get as cool as it used to anymore. Looks like the green-house effect is well under way in Thailand!
The best time to go season wise is in the Thai winter. However this coincides with the other Thai season (tourist or "high" season). This means that Hotels, Air-fare and entertainment all cost more during this time. The Thai "high" season stretches from November through April. You can save significantly traveling in May or June versus December or January. Still, if not a REALLY tight budget, going in January - March seems best to me -- just cause it's nice to get out of the cold about that time.
