HELP! whats happening to my basil

[Suthida]

It’s got brown on the bed of some leavesabd some leaves have a brown dark spots coming up? Is it pest?Is it a fungal disease ?

 

[Marck]

Hello and welcome to the Forum.

Black spots on Basil (Ocimum basilicum) may have several causes, involving pathogens, cultural practices, and temperature.
The pattern I am seeing on your leaves suggests a pathogen of which there are several possibilities.
I would recommend removing diseased leaves and doing what you can to improve culture.
Grow your basil in full sun with good air flow. Water the soil directly without wetting the leaves. You could try mulching the potting soil with fresh bark or pebbles, as this may prevent bacteria or fungal spores in the soil from spreading.
Most chemical controls are toxic or at least distasteful, so I don't usually recommend the for leafy edibles.

If you can post a very close-up macro shot of the patches, that could provide more information. Many modern cameras even on phones can take rather good macro shots, with proper lighting, stability, and focus.