Step 1

Turn on a multi-functional pressure cooker (such as Instant Pot®) and select Saute function. Add oil and red curry paste to the hot pot; saute for 30 seconds. Add chicken and mix well with curry paste. Pour in coconut milk. Close and lock the lid. Select high pressure according to manufacturer's instructions; set timer for 2 minutes. Allow 10 to 15 minutes for pressure to build.

Step 2

Release pressure using the natural-release method according to manufacturer's instructions, 10 to 40 minutes.

Step 3

Unlock and remove the lid. Stir in fish sauce and palm sugar. Stir in onion and bell peppers until well combined. Select Saute function. Bring curry to a gentle boil and simmer for only 2 to 3 minutes to keep vegetables crunchy.