Microservice architecture can be futher extended to cover the Internet of Things. Prior to Microservice architecture, Service Oriented Architecture (SOA) has been used for designing and orchestrating services but with limitation of scaling. Microservice has been reported to be able to scale services better and in order to achieve this services must be in form of loosely coupled. Internet of Things must be considered and included in designing service system today in order to build seamless service system. However, designing and combining Internet of Things with service system is not straight forward as it will introduce complexity to the system especially if it is not designed and planned properly. It is also hard to scale a service system if it is in form of centralized and tightly coupled manner. Therefore, it is important to understand how this problem will effect the service system and find the solution to overcome this problem. Promise theory has been looked as a possibility to be adopted in designing a loosely coupled microservice system for Internet of Things. This paper is about the preliminary studies and works that have been done in using Promise theory to understand and designing loosely coupled microservice architecture for Internet of Things.