You can find cheap airfare to Bangkok and Thailand in general by following a few tips. Finding cheap flights to Bangkok is not too difficult if you take your time and know where to look.
Some of the advice I give can be called common sense but putting all these items together in a checklist as I've done here makes an extremely powerful money saving tool.
1st
I'd like to say that if you're starting your air travel from the U.S.A. I've always found China Air and Malaysian Air to be the cheapest, especially from the West coast. The reason for this is because they both use Taiwan as their main Asian gateway and the Taiwan airport has the cheapest hub in the Orient.

If you want to save even more money on airfare to Thailand then fly into Taiwan with the above mentioned airlines and then connect to Bangkok or anywhere in Thailand using Air Asia.
Air Asia is one of THE cheapest carriers in Asia, it's like the price of a bus ride in the States, CHEAP. You will be collecting your bags because you're transferring to a different airline but most countries are just passed through Taiwan immigration for your connecting flight; just show them your bookings and you’re off.
Remember, if you need to make any changes to your Air Asia ticket, do it on-line because if you call they will hammer you with fees.
I really don't care for the Taiwan airport as many people don't speak English, they have no money exchangers at late hours, and the layovers are typically long.
However, on the flip side they do have REALLY good, cheap seafood and soup restaurants open at all hours of the night but you'll need to walk around to find them.
You can also pay $18 bucks to get inside one of the first class lounge near the restaurant. You'll find anything your heart desires in here; video games, beautiful couches, T.V., drinks, etc. With the money you'll save you can afford the lounge.
UPDATE: Terminal 2 has been completely renovated and looks wonderful with all kinds of stuff to do, I actually like it here now but Terminal 1 still looks the same.
Also if you have more than a 6 hour layover then go to the information center and ask about the free bus tour of Taipei. I went and got to see historical downtown, some awesome temples and shopping. They have one that leaves morning and one that leaves early afternoon.
I realize the above situation may not apply to you so I do have other options and alternatives no matter where you live,

Use Trip Advisor to Compare On-line Shopping Portals.
I use to be a big fan of going to various web sites to check fares but now I use TripAdvisor to find the best deal and compare prices. I do this because it can check many web sites like Orbitz, Hotwire, Booking Buddy and many others for the absolute lowest fare. Plus Trip Advisor has forums, trip reviews and even information on getting the most fun out of your holiday, no other portal does this effectively.
What I do is check TripAdvisor first and find the best prices on cheap airfare to Bangkok (this is what I call my base and point of reference). Then I go to the actual airline website that shows the best price from the portal and enter in my dates of travel there.
Sometimes the airline website has a cheaper price than Trip Advisor. I also check out that airline's web site for any special promotions that might be running since they already had the best price. Occasionally you'll find a real gem.
One time I was following this process and found an airline that had a deal of $999 USD to Asia from the U.S. and once in Asia you could fly to any Asian city that carrier flew for one month, all that for $999 USD price, not BAD!
Fly outside of high season. The tourist high season is from late November to April. The reason this is the high season is because this also some of the best weather that Thailand has to offer. Everything is cheaper during off season.
Also check the Thai holiday calendar to find out what holidays in Thailand are occurring, remember Thais travel on holiday too.
One the best common sense ways to get cheap or even free tickets is to use a credit card with reward points. Use the card for as many cost of living items as you can, if they let you put your rent or mortgage payment on your card, do it; any daily or monthly expenses put it on there. It will build up and perhaps after a year or so you might have enough for a ticket.
I'm currently reviewing some material on cheap airfare to Bangkok and general cheap flights to Thailand. The information looks good but I won't post it until I test it out in the real world and find that it's reliable, then I will share it with you all.
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