hello sujith!!
yes for undergraduate course admission in IIST THIRUVANANTHAPURAM, you need to be qualified in JEE MAINS AND JEE ADVANCE.

The required criteria is that candidate should pass the 12th or equivalent exam with PCM from a recognized board with at least 75% (65% marks for reserved categories). Candidates should also qualified the JEE Main & JEE Advanced 2019 examination.

for pg courses admission Candidates having BE/B.Tech/M.Sc/M.S. or equivalent degree with minimum 60% marks (55% marks for ST/SC/PD candidates) can apply. Candidates should have the valid score card of GATE/JEST/UGC NET.

for more details please see :

https://engineering.careers360.com/articles/iist-btech-admission

thank you and all the very best sujith