I agree with golfnut.
I have just returned from BKK. I stayed at the Tower Inn on Silom Road. Book a double room (by internet it is Bt1500 which includes a buffet breakfast for two). You can always tell your secretary that you want a double room as it is only Bt200 more than a single, a better size room, a decent sized bed, etc. Nothing will appear during her booking that will mention the word(s) gay or gay-friendly. I have never had any problems bringing back a friend (or friends).