Asia - access to another int'l terminal at BKK

I'm on the UA 7AM flight in terminal 2. A friend has a TG flight in terminal 1, departing about 1.5 hrs later. Can he enter terminal 2 with me? I'd like get him into a Star Alliance lounge as my guest. A comfortable place to kill some time.

Will security allow this? If so, will he have to pay the BKK exit fee twice?

T1 & T2 at BKK are connected airside. You can roam throughout the main part of the terminals (where all the lounges are and most shops) - it is only the piers that are restricted to pax on flights from there.

I am not sure if your friend will be allowed to enter terminal 2 after check-in at TG in terminal 1.
It is very easy to walk between both terminals on the check-in area level (same on the arrival and mid/offices levels). Only the domestic terminal is a looooong walk.
Having said that, as Kiwi Flyer pointed out, both terminals are joint together airside and you can then join your friend in any of the lounges. I would recommend any of the TG lounges as opposed to the other *A carrier's lounges.

Your friend should go to terminal 1, check-in with TG, pay the 500 baht departure tax and clear immigration. Now your friend will be airside.

You should go to terminal 2, check-in with UA, pay the 500 baht departure tax and clear immigration. Now you will also be airside.

You can meet up with your friend airside.

Maybe you can use this map (http://www.staralliance.com/startravel/jsp/guide.jsp?airport_selected=true&left=left&country_selected=tha&city_selected=ban) to pick a spot to meet up airside?

Security is done at/near the entrance to the individual piers.

As a final note, the luggage x-ray and pre- pre-screening processes for UA have changed a bit. UA's counter are the very first row all the way to the left as you enter terminal 2. It used to be that you could get 'counter-side' at any x-ray point, using one that was a more to the right with no line, thereby jumping the long UA queue, and get right to the pre-screeners at the check-in counter. When I tried this a few weeks ago I was re-directed back to the long UA line, where they have introduced a pre- pre-screening process. This was ~ 4 weeks ago so, and it was the first time I ran into this problem, maybe it was just a special alert. But do be aware that check-in can take quite a long time, maybe 10-20 min for F/C/*G, 20-40 min. for Y. Save a 500 baht note for the departure tax, it seems like most of the staffed windows are closed at 6 AM and new vending machines are in place.

Thanks so much for the helpful info & map link. From discussions in the TG forum, it seems the best TG lounge is the new, two-level Biz/*A lounge near pier 3 / gate 31. (Complimentary massage might still be offered, too!)

http://www.flyertalk.com/forum/showthread.php?t=326646

As long as we're not running late, it should be a convenient meeting place for both of us.