I have stayed at this property many times and started years ago. I have stated earlier that I felt the hotel was overall better when it was under the Le Meridien brand, even with a little less "luxury" hard product.".
Then, the staff turnover was not so high (New staff can't treat repeat guests the same way as staff that have been at the hotel for a while, especially when the hotel has not recovered the Starwood data), the service at the lounge was better, the Front Desk staff had overall a much better attitude.
The GM has been there for a long time and has a "reputation", that is widely known by staff and colleagues in Bangkok, but, IMO, the issue is more with one of the #2 (the HM position has not been filled up after the previous one left and there are now 2 Executive Assistant Managers).

There are still a few staff members that have been there for a long time and they treat me very well, but after a few awkward experiences, I decided to give this property a long break. I will probably never relive the very good experiences that I had in this property and I am simply better welcomed at some of the other Marriott properties in town, including new ones like the Madi Paidi.