Vodka (as much as you wish)
Herbs of your choice: Kaffir lime leaves, Thai chilies, Thai basil, lemongrass, ginger, etc.
Wash and dry herbs well and let infuse in the vodka for 5 days, out of direct sunlight. Swirling the container once a day. For kaffir lime vodka, use 3 kaffir lime leaves for every cup of vodka; for spicy vodka, use 2 Thai chilies for every cup of vodka.