It depends on the hotel. Not sure does Platinum status matter?
1) I stayed in Pullman Sukhumvit Bangkok and they upgraded my room to a suite and decorated the wall with balloons, bed with flowers and etc and was given a cake and wine/champagne (either one of them but we did not drink as we do not consume wine/champagne). I stayed in this hotel around 5 to 7 times previously.
2) My partner was presented with a birthday cake in the club lounge at Mercure Fortune Bangkok on her birthday. We checked in around 4 days before her birthday but we stayed around 25 days for that trip. This really came as a surprise to both of us during the Happy Hours. The staffs got together and sang birthday song for her. That was our first time in this hotel.
The above 2 events happened in 2017.