SIMBEX is an annual joint maritime bilateral exercise conducted between India and Singapore. This exercise aims to enhance bilateral defense cooperation and interoperability between the two countries` navies. By conducting SIMBEX, India and Singapore can improve their coordination and communication abilities in various maritime operations such as anti-piracy, anti-terrorism, and humanitarian assistance and disaster relief.
Option 1, China and India, is incorrect. While China and India do participate in bilateral exercises, SIMBEX is not one of them.
Option 2, Singapore and Indonesia, is also incorrect. Although Singapore and Indonesia have a strong maritime relationship, SIMBEX is specifically between India and Singapore.
Option 4, Malaysia and Thailand, is incorrect as well. These two countries have their own bilateral exercises, but SIMBEX does not involve them.
In conclusion, SIMBEX is conducted between India and Singapore, with the aim of enhancing their maritime cooperation and readiness in various operations.