In Jakarta, I personally would go with the International Cafe or Table8 at Mulia, Satoo at the Shangri-La, or Sana Sini at Pullman Thamrin.
In Singapore, I would go to Colony at Ritz Carlton, Melt Cafe at Mandarin Oriental, or lastly, Basilico at Regent. I personally really liked Colony though.
In Kuala Lumpur, I would go to the Shangri-La or otherwise Mosaic at the Mandarin Oriental (can't go wrong with the food options at these two hotels honestly).
But honestly, in any of these cities (except for perhaps Jakarta), I would go against eating at buffets and actually trying local food. You'll find a myriad of choices at the hawker centres in SG, though my favourite is Tiong Bahru Food Market.