NickB

This is sensible and my guess is that there would be 90% chance of it happening just like that. When I did my transit and the security guy checking my luggage pointed out the lack of stamp on my BP, I mentioned that I was in transit between DEL and BKK. He scratched his head (figuratively speaking), asked me 3 times "so you come from Delhi and going to Bangkok?", went to speak to a supervisor who seemed happy with it, came back and still was not 100% sure what to do and hesitated stamping my BP (perhaps because he had a different stamp to the one used for BPs?) but finally did it and I was on my way.

In many ways, KTM feels much like India in terms of progress through the airport (broadly similar processes), except that the security is more tense and agents do not speak as good English as an India, which makes communications somewhat more difficult and slow. I have done turnarounds in India and it worked OK (despite surprised looks by the agents) but that was with >2 hrs between flights. With only 65 mins, this is a little more uncomfortable if a security agent takes a little more interest in your case, which could cause you to miss the flight even though they eventually satisfy themselves that there is no problem.

Although the odds are on the side of it working, the problem I would have in the OP's shoes is the downside. If all you risk is just getting delayed one day and you are not in a hurry, then it is worth risking since the odds of encountering a problem are lower than the odds of making it through. However, if time is of the essence and you must catch that flight or dire consequences follow, it is just too risky, imo.