The Soi Dog Foundation (SDF) ("soi" = "street" in Thai) is a non-profit organisation that provides food and medical care for the street dogs in Phuket: http://www.soidog.org/About_Soi_Dog.htm They care for the strays living in temples, beaches and have recently built a shelter to house dogs who have special needs.
This youtube video will give you some idea of their work: http://www.youtube.com/watch?v=s225UClTFhY
A friend of mine is going to Phuket at the end of April, and will be buying and bringing over some boxes of drop-on flea/tick medication like Frontline/Revolution to the Soi Dog Foundation. This is the most cost-effective thing to donate from Singapore, as it's comparatively expensive to buy the stuff in Phuket, and it's easy to pack and check in when you're flying there.
At the pet store I regularly use, these are the prices for a 3-dose box of the flea/tick medication:
Hartz: $20.00
Frontline: $36.00
Revolution: $65.00 (this one contains heartworm, anti-mite and anti-tick medication as well)
If you would like to donate a box or 2 (or 10!
![w00t [smilie=w00t.gif]](./images/smilies/w00t.gif)