Grab Taxi is a popular app for using taxis in Bangkok and serves Nichada. Uber is no longer available in Thailand. Official direction from Nichada is to call the Security line to let them know a Grab Taxi is on the way, but success with this is varied. Regular taxis must use the Main gate and are accompanied by a motorcycle taxi. You are expected to pay 30 baht to the motorcycle taxi for their (mandatory) assistance.