If you're just transiting through Bangkok and not leaving the airport, you likely don't need to pay for a visa at all, as long as your layover is within the allowed time for a transit without a visa. However, if you plan to exit the airport during the layover, you'll need to check the specifics of the visa on arrival process. Since India is eligible for visa-free transit or a free visa on arrival (for up to 15 days), you wouldn't need to pay for a transit visa. If you're unsure about the requirements, Matrix provides visa assistance and can help clarify and streamline the process for your trip.