It depends on your mode of transport. The most popular and convenient way to travel to Thailand from India is via airways. On an average, a round trip will cost you around Rs. 30,000 from Delhi. But the prices can fluctuate, depending on the peak season.
You can also take a road trip to Thailand via India–Myanmar–Thailand Trilateral Highway.
I planned a trip which cost 65k approx for 9 days including flights, hotels, tours, food, cabs, shopping. It was a medium budget trip and we covered Bangkok, Phuket, Phi Phi islands and Krabi. Do DM me if you need help planning or suggestions on places.