I started with one pot of basil from the nursery many, many years ago, and have not bought anymore Thai Basil plants since then. When the plant starts to flower and producing seeds, little seedlings will sprout in some of the pots in my potted garden (thanks to the wind and probably some bees that transports the seeds everywhere!). Sometimes I have to discard the little seedlings, keeping two or three of the healthiest looking ones, as there were simply too many! They are easy to grow and very aromatic. In order for the plant to grow more leaves, trim the flowers as soon as they start to appear. By cutting off the flowers, the plant would concentrate on growing more stems and leaves.
This plant started off from a little seedling I found growing in one of my veggie pots. I replanted the seedling to this container and it is growing really well.
The flower buds are already forming at the tips of the stems. If you want more leaves for your cooking pots, trim off those flowers. This will encourage new growth of stems and leaves. How to trim off the flowers? Cut the stem, below the second or third set of leaves under the flower buds. To collect some seeds, allow a stem or two with flower buds to grow to full maturity. When the flowers have bloomed and dried off, the seeds are ready to be collected.
I have harvested the leaves a few times already, and the plant is sending out more stems and leaves. It is getting bushier, which is what I want!
Happy Gardening !