how to save a dying BASIL?

my basil plant is dying from the bottom of the stem. It’s starting to rot but it still produces weak small leaves. The leaves would easily dry out or get weak even if its just small. It still green but i’m worried that i’m just counting days. i checked for bugs, there wasn’t any. I live in a tropical area which is great for basil.

can someone please tell me how to prevent it from dying?

and can i cut the strongest stem and put it in water for it to produce roots for planting later?

thanks!