Chat Sim Chan-Qi Xing Zhen

PS, New update photos 13 Mar 2015:

This is one kind of easy growing plant, it belongs to cactus family. It is grown in Malaysia and Singapore for for medicinal purposes. It is also
known as Bintang Tujuh, Cancer Plant and Chat Sim Chan. The Chinese name is 七星针 (Qi Xing Zhen).
Contrarily to other cacti, this plant is not succulent, and the cuttings should be planted in a moist soil mixture immediately instead of being left to dry out a couple of days. I got one cut brunch from friend, I planted in a plastic pot filled with moist soil, it grows pretty fast.  First few months, it grows a lot of leaves, thick and dark green leaves, it looks like vegetable...I plug off a lot of leaves, it starts to have flowers soon...Clusters of broad orange flowers, about 7 cm in diameter, bright pretty flowers only last for one day, followed by round fruit in yellow colour about 4 cm long with bracts...
I was told it is one type of herbal plants, the dark green leaves can use to cook soup with meats, but I haven't tried yet.

(Picture was taken in Malaysia many years ago, there is a field for this herbal plants. )
(A view of the young shoot. Sharp thorns arise from the base of the leaves and numbers up to seven in mature parts of the plant. That is where the Chinese name 七星针 coming out)
Some information I could find below: 

Pereskia Saccnarosa: Chinese  name 七星针: This plant is from a cactus family which probably one of cactus species with leaf. It was a primitive genus in cactus family. Pereskia is originated from Korea but can be easily found in Singapore. This plant can live almost any type of condition except cold area. Pereskia is one type of herb good for detoxification and can prevent cancer. It is used to cure cancer especially Colon cancer, Nose cancer and several others deceases. I was told by old people, the leaves can cook with meat to make soup, it is good to prevent cancer, high blood and diabetes.

Where you can purchase this herb plants in Singapore?

Here