For Singapore, you can spend Sunday evening at one of the good restaurants on Dempsey Hill - Jumbo Seafood for their rendition of Singapore’s famous chili crabs, The Dempsey Cookhouse & Bar for some nice cocktails and Asian-European fusion fare by Jean-Georges Vongerichten, or Canchita for Peruvian cuisine.
Dinner times in Singapore and Bangkok usually start between 6pm to 8pm.
Do try and make reservations in advance - it can get really busy in both cities.