Here is the Thai basil

Basil really needs heat--they don't like it if night temps are below 55. For me, it's still not time to plant basil out yet. Looks to me like cold damage. They may survive, but many times just stunt and won't bounce back when exposed to too much cold.

Mine too... we had a week of very warm and then quite cold... browned after the cold!I am in central Ohio, zone 5b!

I agree! You don't say where you are aside from your zone, which would be helpful. But this has been
a crazy May here in central Ohio and basil (like tomatoes, peppers, and eggplant) resent
temperatures below 50 degrees. I just planted all of those plants
yesterday, ahead of a lovely soaking rain.

Were they hardened off before you planted them? Looks like some sunburn to me.