Hey Niyati - go for Vietnam, it is super amazing - Must visit places : The Halong Bay cruise (The Kong Skull Island ) sailing through so many beautiful islands. Sapa - a town in the mountains, with so much greenery all around rice fields ...must visit is Fan si Pan (one of worldest highest cable carts that take you to top of the mountain. Being there and the sight is just like experiencing heaven. Hoi Ann - its a beautiful city(evening the whole city get lit up with Chinese lanterns all around it is beautiful ....i bet you will fall in love with this place. You can also do scuba/Snorkelling from Hoi Ann at the Cham Island and end it with a nice sea food lunch near the beach. Hanoi - The capital of Vietnam, will give you the city life of vietnam, a lot street food and they have flea markets - which are crazy with a lot of shopping options. Hue - visit the dark caves - you do a zipling n then swim n enter the caves ...you have a mud pool inside which is high in mineral....also lot of more caves - like the amazing caves, Paradise cave and the best one it the World's largest cave - Son Doong, but you need to book in advance 6 months and it pretty experience(read about it on google). Ho Chi Minh City - Here you can visit the Chu Chi Tunnel (these are small underground tunnels which were used during the America - Vietnam war(you get a chance to go thru these tunnel and experience it. Also visit - mekong delta, the floating village....its amazing.... There is lots more and i bet you will surely fall in love with this country .....a lot of staying option- backpackers hostels all around(pretty cheap charges).
Hi Niyati, All the other options given below are great but you can go to Sri Lanka hassle free. Just purchase ETA online and don't have any visa hassle at the airport. Note: What are the Fees and Costs to Apply for a Sri Lanka Visa for Indians? $20 USD. IF you're visiting for business purposes and need multiple visits, the fee is $30.
List of countries which provide Visa-On-Arrival for Indian Passport. Thailand
Timor Leste Laos
Kazakhstan Good Luck!!