In May 2021, there was a COVID-19 outbreak on board a construction support ship traveling from India to Thailand. Controlling the outbreak on this offshore vessel from 11 May to 2 June 2021 was applied. This case report describes the teamwork management of COVID-19 control on the vessel in the Gulf of Thailand. We summarized the COVID-19 outbreak control process on board, including active COVID-19-infected cases (CoIC) and close contacts (CoCC) identification, isolation, quarantine, treatment, and clinical monitoring using telemedicine to report their health measurements twice daily, including emergency conditions if they occurred. Active COVID-19 cases were identified by two rounds of reverse transcription polymerase chain reaction (RT-PCR) tests in all crew members, in which 7 of 29 (24.1%) showed positive results. Both the CoIC and CoCC were strictly and absolutely isolated and quarantined on the vessel. No serious medical conditions were reported during the monitoring. The third-round RT-PCR tests were conducted, and all tested negative one week later. Teamwork management in proactive COVID-19 case identification, isolation, comprehensive treatment, and close monitoring of health conditions using telemedicine devices is beneficial for controlling the COVID-19 outbreak on board.