only time I go for vacations with somebody is when I go for an organized trip where everything is pre-arranged and need for quarrels of what to do is thus eliminated.
If you go alone you're free to do what and when you want and meet whoever you like.
Particularly in Bkk when you certainly will be meeting some companions you would be rather discreet about.
Few years ago I was in Bangkok with a straight friend for a week but we had an arrangements that we part our ways after breakfast and none of us will bring any companions to hotel room we shared. He was whoring at Nana Plaza and soi Cowboy, I was at Patpong and to this day he doesn't know what side of Patpong I was frequenting.