I admire OP's dedication to go through the hassle even if just for the shot glass. I collect them (shot glasses) from different places that FT has helped me to travel to, and it is always a great reminder of your time in different cities. As mentioned by other FTers, use the train. Much better than hedging your bets on Bangkok traffic. And keep a window open for security clearance when coming back. I flew BKK-PEK in Aug and just clearing security took 55 minutes. Check-in, immigration and getting to the gate combined took less time than security.