The journey from Kullu to Thiruvananthapuram is a massive 3000 km trip. You must take a bus to Delhi and then a long-distance train like the Kerala Express to Thiruvananthapuram. The train journey from Delhi to Thiruvananthapuram takes about 45-50 hours. This route connects the Himalayas to the southern tip of India. Expect a total travel time of 65-70 hours including transfers.
Total Distance: 3000 km by road, 2500 km air distance.
Kerala Express is the most direct train option.
October to March for pleasant weather in Thiruvananthapuram.