I have to concur with luxury. If the OP can stretch his budget just a little bit more, he can stay at the Rajadamri Suite at the Four Seasons, which we found to be an incredible value and our favorite property in Bangkok. 3,700 square feet including a large dining room with kitchenette; beautiful, spacious and comfortable living room with three sitting areas (two on the corners, one in the middle facing the plasma television); study with a large work desk, telescope and card table; and a fantastic bedroom. The B&O sound system in the living room is connected to the dining room as well, so music is seamless when entertaining. The study and bedroom have their own entertainment systems. There's also a large walk-in closet, marble bathroom with a Jacuzzi bathtub (and 2 powder rooms), and a massage room connected to the bathroom (with a separate entrance for the masseuse).

The service is nothing less than extraordinary. We were greeted by the General Manager at the driveway when we arrived, who walked us through the lobby to the elevators. Her assistant managers took us upstairs to the room, and did an efficient in-room check-in while giving us a detailed tour of the suite. The F&B manager personally oversaw our catering, as we had a dinner for friends and family in the dining room. They even organized a magician and clowns and decorations for us as we were celebrating our daughter's birthday. Fantastic service and very reasonable prices, part of the reason why we love Bangkok!

Though this could be a bit too much space for a couple, I'd say why not? What a perfect room for an important anniversary, and a fantastic way to end a trip!