Apple Watch SE

While the Watch will operate in India, you will not be able to activate cellular on a US Watch in India. You would need to purchase the model for India, they are two different models and the model for India is not available in the US. See this for what model needs to be purchased in India to have the cellular activated, as well as the model number for India. Apple Watch - Carriers - Apple

A cellular watch bought in the US will only function in North America,Canada,Mexico and Puerto Rico anywhere else it will function as a GPS only watch.