The conversation between Ongsa and Nakhun's mother seemed light and fluffy on the surface, but underneath it was very telling about this world, and I appreciate the attention to detail it provides.
For one, this is a small community. This is not the majority of people in Thailand, or the world, this is a small in-group, where children are raised fully understanding the social norms and customs, and a great many of the people in the culture already know one another, or have a kind of friend-of-a-friend connection to most other people (for example Sangnuea and Naphitch only met this episode, but it was inevitable with their multiple connections through other people).
Phatsa was excluded from this information, and this community, in the way he was raised. We don't know details until next week, but it looks like it was very deliberate. My guess is that his dad is not part of the world, and was possibly trying to keep Phatsa protected from it - maybe related to what happened to his mother, especially if she was also a true omega, and that caused conflict.
This also makes it seem likely that when Ongsa first met Phatsa, he picked up that he probably belonged to their world, and was trying to gently introduce him to it. Made friends with him, started bringing him to the cafe, which was patronized by a lot of people in their community, and then gradually talking about their world and encouraging him to get tested. He tried to make it sound normal, and no big deal, because he wanted Phatsa to feel ok about it all.
I know it's more fun to go "bwa-ha-ha all these random people talking to each other about this stuff", but there are actually a ton of context clues here that this is a community, and Phatsa was cut off from his birth culture.
And that's part of what makes Phatsa's experience so brutal, because not only is he having to cope with this sudden "soulmate" situation, but there are going to be constant reminders that make him feel like an outsider.
