I've just looked into this for a friend of a friend that was hoping to move here. Am pasting below what I sent to her:
I have spoken with a friend who used to assist a little boy with Autism in a mainstream school. She says that, if possible, put your child in mainstream education this way. You will have to fight to get him a place!
She also says Dover Court has reputedly the best (only?) Special Needs Unit. I have also searched the archives of ExpatSingapore.com and found recommendations for these schools as mainstream education for children with special needs:
Singapore American School (SAS)
Tanglin Trust School
Australian International School
Autism Support Groups:
[email protected]
[email protected]
On ExpatSingapore, look out for a member known as "$0.02". She organises SN coffee meetings for "a group of parents with a Third Culture special needs child (or children). The Group offers friendship and support."
(Note: I contacted this person myself and she was very helpful.)
More local resources:
http://web.singnet.com.sg/~autism/index.htm
http://www.autism.org.sg/public_html/html/about_arc.htm
IIRC, the friend of a friend visited Dover Court and was impressed but the waiting list for her child's age group was large and she decided, for the time being, not to move.