Briefly now,
1) Royal Orchid Sheraton - mixed feedbacks on overnight guests; far from BTS stations because of its riverside area location; but the accomodations are great! You can get a room here for a low as US$94 per night at
http://www.accomline.com
2) Holiday Inn Crowne Plaza - mixed reviews on overnight guests; relatively near to a BTS staion; rooms here can be had at US$60 per night incl. bfast.
3) Monarch Lee Gardens - mixed reviews on overnight guests but it seems to be the most tolerant among the four; relatively near to a BTS station; it's also the cheapest among the four where rooms can go for a low as US$50 per night incl bfast.
4) Amari Watergate - mixed reviews on overnight guests but their gym is cruisy; front desk staff tends to look down at Thai off-boys; relatively inconvenient for walking if proximity to a BTS station is a priority; good accomodations, though, with rooms going for as low as US$65 per night incl bfast.
Yorkie, if budget is an issue, then try these other hotels which are comparatively more gay-friendly:
On Sukhumvit: Amari Boulevard, Novotel Lotus, and as you earlier posted, Landmark Hotel (renovations notwithstanding) because rooms here are currently valued between US$40-50 per night incl. bfast.
On Silom: Try the serviced residences and I'm sure you won't have a problem here. Always toppping my list is SalaDang Place
http://www.saladangplace.com where studios can be booked at less than US$40 per night incl bfast or Saladaeng Colonnade
http://www.andrewpark.com which is a little more pricey at US$65 per night incl bfast. These two are so convenient to both BTS stations and the gay nightlife of Bangkok.
Good luck to your search! Tell your secretary that she can do better than offer you these selections.