Thai green curry is coconut milk based: green curry paste fried in the thick cream skimmed from the top of unshaken coconut milk, then protein and vegetables simmered in the remaining coconut milk, balanced with fish sauce and palm sugar.
Coconut milk technique
Open the can without shaking. Scoop the thick cream from the top into a hot wok; fry until the oil separates and the cream cracks (looks like broken sauce). This cracks the emulsion and releases the coconut oils to fry the curry paste. Add the paste to this hot fat; fry 2–3 minutes until fragrant. Then add the remaining thin milk.
Thai basil timing
Holy basil (krapao) or Thai sweet basil (horapa) is added off-heat, immediately before serving. The residual heat wilts the leaves but preserves the volatile aromatics. Adding basil to a simmering curry drives off its scent within seconds.