1.5 hrs is enough buddy.There is no need to panic and it should be manageable.I can understand the anxiety if this is ur first international trip.You can always request the airlines/airport people to allow u to move forward in the queue if u feel u r going to miss the next flight.
Animesh, it's certainly not my first trip, I have traveled a bit if not a lot and am aware of immigration process, it's just have read sowny diff and conflicting reviews regarding Thailand immigration, so am skeptical. selfies and shopping can wait till later.
Well if you travel frequently by now u wud have realised u can go through immigration process in 90 mints.Yes its not enough considering u want to get some pics clicked at airport,do some duty free shopping or have something to eat.But if you just want to go through the immigration process,it should