This picture could help. There are 5 types of Basils that use in Thai cooking: Sweet basil, Lemon basil, White holy basil, Red holy basil, and Wild holy basil. Lemon basil use extensively in The North and Northeastern of Thailand. Sweet basil usually use with curries and dips, or eat with noddle soup, and Holy basils use for stir-fry or soup. Have fun cooking.
Classical Thai cooking by Chef Phant.