It can be a plural form of "Kāyo" the "accusative"?

[alalfhr]

“Pali Noun Declension Table 1 x A 4 Bolt” in the chart comes out like this.

nominative. masculine. singular. o

nominative. feminine. plural. āyo
accusative. feminine. plural. āyo

[sujato]

No, because it’s masculine.

You can, however have say kathāyo, from the feminine kathā.

[alalfhr]

Thanks for the friendly answer Bhante Sujato.