I transit through both airports on a regular basis. If I have a 4-5 hour transit, I would definitely choose BKK over SIN, just because of the TG lounges over SQ lounges. In SIN, Star Gold status only gets you access to the SQ Kris Flyer lounges, which don’t have showers. After a long flight there is nothing I would like more than a shower before the next leg/flight. SQ Kris Flyer lounges in SIN don’t even have toilets inside. You have to walk outside the lounge and use the public toilets, which is not very convenient. The TG lounges in BKK have showers and some cubicles with beds that you can nap in.

The one thing I don’t like about BKK is that on arrival, you have to go through security before you get into the departure area. The problem with this is that if you arrive at a busy time, the security line can be very long. And if you have a short layover, it can be a problem. When you arrive at SIN, you walk out to the departure area and you only do security at the departure gate. So it is a much shorter security line.

If you have a longer layover SIN can be nice because it is very convenient to put your hand luggage in left-luggage (storage) and take the MRT into the city. You do have the same thing in BKK, but somehow I trust the Singaporean transport system to work of efficiently and punctually. There is also the new Jewel Changi at SIN, but I think it is just an overrated mall.
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