Pour the vegetable oil in a small saucepan and add the chopped onion and garlic. Place this over medium-high heat.

Cook the garlic and onion for 3 to 4 minutes until the onion starts to soften. Then add the palm sugar (or brown sugar), the fish sauce, the tamarind juice, the oyster sauce and the hot chili sauce. Pour in the half a cup of water.

Stir and bring the sauce to a good boil. Let it reduce by half until you get a fairly runny and sugary thick and sticky mixture. This is your pad thai sauce. Take the sauce off the heat and put it aside until needed later.