I just finished my glorious Thailand trip and I can tell you the following:
1. We did 2 nights @ Peninsula BKK in a Duplex Suite. All I can say is WOW. From the moment we walked out of customs to the moment they escorted us back through airport check-in when we left, we felt like VIPs. The airport transfer service is a must, and a great deal to boot.
We were greeted by name at the door upon arrival and whisked directly up to our suite for in-room check in. This is the first hotel that has done in-room check in for us, and we've stayed at some pretty amazing places, including Georges V in Paris. Welcome fruit, tea, pastries, etc...Facilities are top-notch, the hotel is large but quiet. Staff is incredible (though the restaurant staff are a bit on the slow an inattentive side considering how good everyone else is). The riverboat service is super convenient and really made a big difference in our stay. Breakfast is included if you book through Virtuoso or Amex PTS, and it's quite substantial. There's an amazing mix of tropical fruit, western breads and pastries, eastern noodles & stir-frys, eggs prepared several ways, etc... We did not try the spa, but we went inside and it looked quite nice. You must visit the 37th floor heli-lounge (direct access from our suite), as it's spectacular.
I would definitely pick the Pen if we went back to BKK (though I might not spring for such a ridiculously large suite (3500 sq. feet).
2. Four Seasons Tented Camp Chiang Rai - by far my BEST hotel experience in the world, ever. Arrival by boat is included in the lofty price and is an experience not to be missed. Michel the resident manager makes an effort to greet each new arrival and he literally will sit and chat with you about all kinds of things if you like.
Food and drink is also included (the entire resort is 100% all-inclusive, right down to a 90 minute spa treatment), and it's quite good. You're literally in the middle of the jungle, yet the staff is somehow able to do a better job than any city hotel I've ever visited. Everyone learns your name and food/drink preferences almost immediately. Service is damn near telepathic and they seem to anticipate nearly every desire.
The elephant experience is almost life changing, and is quite fun. Who knew these giant creatures were so gentle and intelligent. The tour guides are super-knowledgeable and also quickly learn your preferences about what you enjoy seeing and doing. They even carry your shopping bags for you. The bugs are omnipresent and bug repellent is a religion here, but as long as you constantly reapply you'll do just fine.
We only stayed 3 nights because that's what most people on tripadvisor said to do. I easily could have spent 4 or even 5 nights here.
A word of advice: Rack rate is over US$2140 per day (no joke); if you combine your stay with a few nights at either FS Chiang Mai or FS BKK you get a drastically reduced rate. However, we were able to negotiate a reduced rate directly with Michel of about $1750 per night, with no requirement to stay at other FS properties.
3. Trisara - what a paradox this place is. The facilities are first class all the way, and the villas are simply spectacular. When you're sitting out on your patio overlooking your private infinity pool and the Andaman Sea in the background you simply think "I've arrived, and I never want to leave". The food runs the gamut from good to excellent, and the spa treatments are quite nice (if not a ridiculous ripoff even by American standards).
However there is a dark side to my dear Trisara: her staff. They try really hard - perhaps harder than most places, but they are simply not five-star caliber. There are the de rigeur touches of cold towels and water bottles everywhere, but they can barely speak English and misunderstood us probably 30% of the time. There is no proper concierge, and the staff is unable to provide any recommendations beyond the pre-written guidebook by General Manager Anthony Lark (of Amanpuri). The personal waiter who took care of us during our romantic in-villa BBQ was hovering near our table the entire time and kept wanting to make mindless small talk to show off his limited English. He was sweet and had a kind heart, but it was slightly disruptive and it definitely kept a 5-star experience from being truly 5-stars.
The other severe negative about Trisara is its location. If you're the type to just lay out on the beach and get spa treatments all day, then fine. But if you like to go out and sightsee, shop, go to other beaches, etc...then it's a minimum of 20 minutes to get to the closest place and up to 45 or 60 minutes to get to the more populated and busier areas.
I suspect for a first time visit to Phuket it might be better for someone to stay at a slightly larger, more centrally located resort like the JW or perhaps at a resort that offers more than 1 dining option like Banyan Tree or Amanpuri.
YMMV