[MENTION=150230]Kalboz[/MENTION]
Great reply, thanks! Though I spend close to 200 nights/year in hotels, I neither have any relevant status nor credit card benefits. That's one of the downsides of moving to Europe and working in smaller cities with spotty chain coverage. I do have plenty of FF miles, but they give much better value for flights.
Just to make sure that there's no misunderstanding, the $1350 I mentioned for the Okura was for 6 nights, so after cashback it's like $200/night. I assume when you said I could get the Authors' suite for that kind of money, you meant for one night, right? Cheapest I have found doing a quick search was close to $1000/night.

As for the St. Regis, I would get potential upgrades, breakfast and early/late check-in/out, but no executive benefits beyond that (i.e. lounge). The only property where I would get lounge access is the Marriott. While this is a nice perk, it's not that important to me since I'm planning to mostly eat and drink out.
However, I really do value a good hotel breakfast. It is my impression that none of those 3 would disappoint. Some of my colleagues actually told me that they were a bit disappointed with the spread at this St. Regis. But when we worked in Japan for a week, they basically lived off McD since they didn't know what else to eat. For all I know they were probably disappointed because the spread didn't include Quarter Pounders.

So if I were willing to spend around $200/night with decent breakfast for 2 people, what do you think would be smarter than the Okura? I was also thinking about spending the last night at the St. Regis in order to get some first hand experience for potential future visits.
My girlfriend seems to be really into the Okura, so it is somewhat of a preference, but of course I am interested if we would get something much better for the same amount.

I have been to Bangkok before, but it was for a wedding and only for like 3 nights, I spent most of the time with celebrations and being jet lagged. So I guess the answer to your question would be technically yes, but not really.