For the spice paste, grind all of the spice paste ingredients to a paste in a mortar and pestle. Set aside.
For the vegetables, heat the vegetable oil in a wok over a high heat. Add the spice paste and fry for 2-3 minutes, or until fragrant.
Add the lemongrass, bay leaves, galangal, ginger and kaffir lime leaves, then pour in the coconut milk and bring the mixture to a simmer, stirring well. Simmer for 5-10 minutes, or until the coconut milk has reduced in volume and thickened slightly.
Add the green beans, carrots and shallots and continue to simmer for a further 5-10 minutes, or until tender. Add cucumber and chillies and simmer for a further 2-3 minutes.
Stir in the rice wine vinegar, sugar and salt, and continue to simmer for a final 2-3 minutes. Check the seasoning, adding more vinegar, sugar or salt, to taste.
Just before serving, remove the lemongrass stalks and bay leaves. Serve in bowls.