Happened to chance upon this post on Singapore Farm today.

Our Orchid Farm is open for families to visit too.
Open to public, no admission fee. ^_^

Location:
Toh Garden
11 Lorong Pasu,
Sungei Tengah Agrotech Park,
Singapore 699191

Contacts:
T: 6763 9186
W: http://www.tohgarden.com/
E: [email protected]

Operating Hours:
8am - 5pm Mon - Sat
8am - 3pm Sun

How to get there:
Bus 975 & Bus 172 from interchange @ Lot 1 Shopping Mall
http://www.tohgarden.com/contact-us/