The best recommendation I can give you for Bangkok is to get together with other board members who live in Bangkok. If he is in town, Christianpfc is usually quite willing to meet and usually would be delighted to personally take you around. He's in your age bracket too. He is located closest to the Malaysia Hotel. Don't miss his blog:
http://christianpfc.blogspot.com
Send him a PM: christianpfc
As far as I know, the two most popular choices for gay-friendly hotels in Bangkok are:
Malaysia Hotel:
http://www.malaysiahotelbkk.com - basic rooms, but very gay friendly. I always stay there when I'm in Bangkok
Pinnacle Hotel:
http://www.pinnaclehotels.com/lumpinee - on the same street as the Malaysia Hotel - more upscale - I stopped staying there because if you want to take a "guest" to your room, you either have to book a room for two or pay them a joiner fee.
Tarntawan Place:
https://www.tarntawan.com - Closest to the Silom-Surawong gay bar area
There is also the BBB Inn:
https://www.booking.com/hotel/th/bbb-inn.html - I have never stayed there and I don't know anyone who has.
For cruising, we have a topic on this board. See:
viewtopic.php?f=3&t=7808
I agree with Windwalker. Check the other two major gay Thailand boards too. On the Gaythailand board, go to the Gay Thailand forum. Once there, go to the search box and type in Saranrom. Loads of topics will come up about places to cruise.
As for what to avoid, your personal safety shouldn't be a problem because you're most likely going to be in the major tourist spots and they're always crowded. What I would be watching for:
1. Don't take taxis if the driver refuses to turn on the meter. If the driver won't use the meter, just get out of the cab.
If you're not afraid of them, I recommend the motorbike taxis. Most of them are very honest about their fares and they will get you where you're trying to go much faster than regular taxis. They're excellent at weaving in an out of traffic.
2. Be VERY careful about pickpockets. If you're going to be a crime victim, that's the most likely thing to happen to you. I advise carrying no more cash than you expect to need when you go out, and carry it where pickpockets can't get at it.
3. Street touts. The gay go-go bars usually have boys outside trying to get you to come in. They're harmless. But
any other street touts - don't even let them talk to you. If you are approached by anyone, ignore them just as if they aren't even there and keep right on walking.