Hi Lia!
I googled for my obgyn and got lucky as we like him very much.
You can also go to the Singapore Motherhood Forum. They have many reviews on all the obgyns in Singapore. However it is a very messy website.
If you want someone who is pro natural birth and is willing to discuss your birth plan, I've heard Dr Paul Tseng at Thomson Medical Center is highly recommended.
For hynobirthing, go to
www.fourtrimesters.com to find out more.
Again, the website is a little messy and outdated but I had a session with Ginny who runs the place and will be attending her course on hypnobirthing.
Hypnobirthing is essentially the belief that a pain free drug free birth can happen. The course teaches you to prep for delivery through breathing, mind control, support from your partner etc. I guess you would wikipedia or google for more info.
Good luck looking for a doctor