If you agree with this, you should take into consideration not only the killed person's age, but also their health, wealth, quality of life, marital status, social standing etc. etc. ad infinitum.
I was told at a local 7-Eleven that payment by credit card is only possible for amounts of 200 baht and up. Like in good old pre-covid days. Is that what they call cashless society?
It doesn't mean they did that lawfully. Anyway, I don't know what exactly you told them, how you answered their questions. I've been questioned many times, and always allowed in.
I've been in Thailand as a tourist since the beginning of 2020, never leaving for more than a few days. As long as I don't stay longer than each stamp allows, it's not a problem.