Indonesia is not a party to the Hague Service Convention, and it has no service treaty with the United States. According to the U.S. Department of State, in the absence of a prohibition, service in Indonesia may be made by mail, by an agent such as a local attorney, or through Letters Rogatory sent through diplomatic channels. Which one fits depends on your court's rules and on whether you may need to enforce a judgment in Indonesia.
Letters Rogatory are the formal route: a U.S. court's request, transmitted through the State Department to Indonesian authorities, which typically takes a year or more. Service by a local agent is far faster and, in federal cases, is generally supported by FRCP Rule 4(f)(2) where Indonesian law doesn't prohibit it. If enforcement in Indonesia is likely, take advice from Indonesian counsel before choosing the method.