Go to booking.com put 3 people and then see if you can add another person to the room by paying for extra bed or you can check the capacity max for each room and you’ll be fine
I was told in my embassy that only the company you work for can make a sponsor letter so only relevant for remote workers. But why would a company would sponsor you to work remotely in Thailand if you are not allowed to do business with Thailand 🤷🏻♀️.