Ask ur relatives in Singapore

they should be able to give you better advices as people in Southeast Asia often travelling around neighboring countries - they know where best to eat and shop, plus other activities.

Thailand - Bangkok and nearby beach Pattaya, (about 1.5 hour away) should be good enough for your purposes.
Bangkok is a very busy city, lots of temples, local markets as well as ultra modern skyscrappers and shopping malls. The problem with Bangkok is the city is sprawling and traffic is horrible. To avoid traffic jam use the river boat to get around, dirt cheap and much more fun than travel by taxi and stuck in traffic jam.
here is an introduction of the river boat.
http://www.into-asia.com/bangkok/boats/

Dont go to China Town in Bangkok unless you enjoy total chaos and very dirty and crowded streets.