I can only speak for BKK but for my stays I've only really done Athenee Hotel - Luxury Collection and it was a fantastic stay (multiple stays for more than 3/4 nights):
- I loved the location its close station (Phloen Chit - 5 minutes walk) and its a quiet area
- The lounge is fantastic and extensive (with a great breakfast option as well as a bar - for coffee/drinks)
- Breakfast downstairs was great - multiple cuisine (e.g. Thai/Japanese/Chinese/Indian/Western)
- Probably the only hotel where my YOUR24 request is almost always (~90%) guaranteed/upheld (even with a suite upgrade)
- Upgraded very frequently and even given drink coupons/vouchers