Hartford, CT to Delhi, India via Bangkok, Thailand - What Happens at BKK Airport
 

Assuming we check our bags through to Delhi (I checked with United - they say it is ok to do this), will we have to go through immigration in Thailand or can we go directly to our Air India gate and check in? Would we have to pay the airport departure tax?

topping - Kathie, anyone?

You will not go through immigration or collect your baggage, as you will be “in transit”. If were not able to check-in and get boarding passes for your Air India flight while you were at one of your US aiports, then when you land in Bangkok, go to the transfer desk for Air India and get your boarding passes for the flight. (Not sure if Air India has an counter in any of the US airports you will be in, if they do, it is worth trying to get boarding passes in the US, as lines at transit counters can be long.) There is some shopping and some restaurants to spend your time in. If you have a very long layover, you could get into Bangkok, write back if your layover is more than 6 hours, and people here can give suggestions for a very whirlwind tour.

You should have no issue with checking your bags all the way through. Don’t confuse airline alliance programs with the worldwide agreement of all airlines to transfer baggage from one airline to another. You do not want to get involved with having to go through immigration, collect you bags, and then re-check in everything in Bangkok.

i don't think you will pay the tax as this is done in the outer lobby before immigration checks...

No tax to pay, as Cicerone says you will be 'In Transit', just go to the main transfer desk in the transit lounge to get your boarding cards if you can't get them in the USA. In this case also show them your baggage tags as they usually then grab the radio and make sure your bags are transferred OK.