The way I see it, there is clearly a difference between the official guideline published on the website of the Bangkok immigration office for the the issuance of a non-O visa for a dependent of a "person having residency in Thailand (non-O) " by an immigration office and the way this guideline is interpreted and implemented by some immigration offices.
One question that has been brought up is whether "residency" as used in the guideline is perhaps meant to refer to what we know as "permanent residenccy".
As "residency" is used here in the context of a "person having residency in Thailand (non-O) " and as "non-O" is a short form for "non-immigrant visa category O", used not only on this forum but also on the websites of the Ministry of Foreign Affairs, Thai consulates and the Immigration Bureau, "residency" in this context cannot mean "permanent residency" because permanent residents are in Thailand not on the basis of a non-O visa, but on the basis of an immigrant visa or a non-quota immigrant visa.