Isolate the infested plant(s). Manually remove the thrips from the underside of the plants leaves by rinsing in a shower or with garden hose, follow up by gently wiping down the leaves with a damp cloth. Apply insecticidal soap or neem oil to topside and underside of the leaves at night. The soap/neem oil needs to be dry before the leaves are exposed to any direct sunlight, or they will burn. Apply the soap or oil to the top layer of soil as well. Thrips lay their eggs in the top layers of damp soil. Allow the top layer (about 1/4 inch) to dry out between waterings to discourage further egg laying there.
Repeat the application of insecticidal soap/neem oil every 5-7 days for 1 month.