I fail to understand how he could get away with it so long. Thais know Farangs who look for this kind of sex face large jail terms when found out. Thais know now-a-days this is not acceptable behaviour, while maybe decades ago this wasn't common knowledge.
I fail to understand namely that no-one knew about this. You can't hide the fact you are looking for kids. If I were to see a Farang male in Pattaya, or in the country side, and most days when I see him he has Thai kids with him, then this is a warning flag. You can soon find out if it are his own kids or not, if they look mix-raced, else it is something to closely monitor. And I bet in 90% of cases your initial instinct will be right.
Eventually he has been caught of course, just so hard to understand why it didnt happen last year, or the year before that.