The Republic of Singapore Navy (RSN), Indian Navy (IN) and the Royal Thai Navy (RTN) conducted the 3rd Singapore-India-Thailand Maritime Exercise (SITMEX) from 15 to 16 November 2021 in the Andaman Sea. The exercise involved the RSN Formidable-class frigate RSS Tenacious, the IN Kora-class corvette INS Karmuk, and the RTN Khamronsin-class corvette HTMS Thayanchon.

As the host for the exercise this year, the RTN led the conduct of the contactless, at-sea only exercise. The participating ships executed manoeuvring drills, communication exercises and naval warfare serials. Similar to last year, this year's exercise was planned virtually due to COVID-19 restrictions, and there was no physical interaction between personnel from the participating navies during the exercise.

Commanding Officer of RSS Tenacious Lieutenant Colonel Tung Wanling highlighted that the successful conduct of the exercise is testament to the long-standing ties established amongst the navies. She said, "The ability to plan and execute the serials virtually is a strong reflection of the mutual understanding and strong partnership that we have developed over these years. In spite of the COVID-19 situation, like-minded navies must continue with our interactions, such as through SITMEX, to deepen our shared understanding of maritime operations, bolster defence relations and enhance cooperation."

The crew of RSS Tenacious served a restriction of movement order and tested negative for COVID-19 prior to deployment.