I also like to differentiate between service and hard product. I'd say the Bangkok St Regis is stronger on hard product than soft, but neither were really where they should be for Bangkok given the alternatives available.The hard product is clearly that of a luxury hotel (vs. that of the SGS for example, which in places looks a bit cheap), but it's a bit smaller, worse designed and less attractive than any other St Regis I've been to. In my Metropolitan Suite for example, the living room felt small and slightly claustrophobic from the lack of decent windows. Downstairs the venue is obviously expensive, but the bar and living room area are (in my opinion) really badly designed and not conducive to inspiring anyone to sit there. The hotel is slightly reminiscent of one of those super expensive upper East Side restaurants that has deployed $5M in marble but which nobody actually goes to.

In terms of the soft product, the upside as I mentioned was that now the staff were trained to a level where nothing went wrong - and the Butler was genuinely good at his job. The rest of the staff were very transactional - no evidence of either warmth or the ability to anticipate and meet your requirements. I would not call the service good - merely that it was no longer unacceptable. Contrast that with the Peninsula whose staff always seems to effortlessly be one step ahead of anything you want, or the SGS staff who every visit seem to come up with new and unexpected ways to make you feel welcome and to go the extra mile.

This is clearly off thread, but if I could stay anywhere for any budget in Bangkok I'd probably stay at the Mandarin Oriental, though I can understand why it's not for you. The Siam looks beautiful but is just too far out of the way of the places I go in Bangkok to work for me, plus given other options it's priced too high for me to consider in Bangkok.

I stay 10-20 nights a year in Bangkok and have adopted the SGS as my home away from home with a level of service and welcoming that doesn't exist anywhere else, but I'd recommend the Peninsula for you if you are looking for a stay in the city more aligned to luxury stays elsewhere. As an aside, if you want to see a review where I really hate somewhere go check out what I had to say on the Park Hyatt Bangkok.