This is generally one of the catches when using eSIMs through someone like Airalo - you don't know where the SIM is from, so you don't know where the traffic is going to be routed via as they almost always route back to the home country. eg, the Moshi Moshi eSIM for Japan was, at least when I had it, actually a SingTel SIM - so all traffic was routed via Singapore.

Thailand is one of the few exceptions for that. The SIM is clearly advertised as being dtac, who are a major Thai telco, so you know it's going to be local. I don't know that I did any speed tests when I was there, but the speed was plenty fast enough for general use.