As you come in, on the left and right sides of the main immigration queues there is a transit immigration desk.

Hmmm... And this is required for international-to-international flight transit? If so, do they also stamp on your passport? A transit stamp?

Its not required, and sometimes those desks are not staffed anyway, so you can/have to go thru the regular lines (but they are usually longer). Nothing is stopping you from that. But be prepared to get the whole half page "permit to stay for 72 hours" stamp there. At the transit desk, all you get is a small octagonal stamp.

Flew KTM-BKK-PEK-ULN and did not need to recollect luggage. However...

Yes, you need to go through the passport desk, even for International-to-International transfer. There is a special transfer line, and yes they do stamp your passport with a transit stamp (octagon shaped IIRC).

A few weeks ago, I traveled on a United issued award ticket and transited (international to international on the same PNR) thru PEK T3 without having to collect my luggage.

BKK(TG) ~ PEK ~ SFO(CA)

I had no problems checking my bag to SFO, but was unable to obtain the PEK~SFO boarding pass while checking-in at BKK. However, I had no problems getting the BP printed from the transfer desk in PEK T3.

The PEK T3 transfer desk agent just asked to see my baggage claim stubs and my passport. A few minutes after locating the proper BP cardstock, I only needed to take a few steps to queue up for the transit immigration line.

You do NOT need to fill out the Arrivals & Departures slip if you're just transiting. I received a red hexagonal shaped stamp in my passport, and proceeded thru a corridor and down an escalator, which put me at the front of the passport check queue for the security screening lanes.

No problems with the luggage arriving at SFO. In fact, it seemed like the *A Priority tags actually did some good (or maybe I was just fortunate)... my bags were among the first dozen that came off the belt.

somewhat like international-international transfer procedure in Canadian airports, where they also put a stamp in your passport.

I asked 3 times and was Told not need to reclaim luggage for the transfer from air china to Thai airways . Luggage tag shows a air china from lax to Peking than TG from Peking to Bkk.

Keeping fingers crossed.

Do they have a left luggage office in case you have a long layover (12 hours) and want to go into the city?

There is pretty cheap left luggage on the bottom floor, head towards the McDonalds in the far corner

I did EWR-PEK-TPE bag checked all the way to TPE

I don't think there's anyway around it. This past summer there were IRROPS on my PEK-SFO UA flight, so they pulled me off the plane for the PEK-ORD flight, and I STILL had to go out thru immigration, come back in, and go thru security again. GS was great in expediting the process, but phenomenal bureaucracy for effectively just walking between adjacent gates with my carry on.

At PEK, luggage can be checked through regardless international or domestic connection.

At PVG, you need to reclaim luggage and re-check for an international-domestic connections in either direction. Never done an international-international connection at PVG. I believe that it has something to do with the airport. I once had a domestic-PVG-international on MU, and had to claim luggage and re-check it.

At KMG yesterday, checked in and asked for tagging of my bag from KMG thru PEK to SIN, first on CA then SQ, staff unable to do so. Thus, I requested Priority Tag for my bag.

Landed 15 mins late, was parked at tarmac near T3 so wasted more time with bus and stuff. Dashed to domestic luggage belt only to find no bag yet. Waited for 10 mins at least to see my bag out as the 1st bag (lucky) of my KMG-PEK flight.

Dashed to T3 SQ counter, checked in, went thru the train, the customs and security as quick as possible (pick the shortest queue) and arrived gate in time for boarding.

If I were not a *A Gold, no way I can make it with all the crap they have in the luggage when ppl boarded the KMG flight to PEK. No way.

So the point is, schedule a longer transfer than what I had, which is only 2 hours.