A WAP (wireless access point) is only a conduit, basically no more significant to your IP addressing scheme than the wire/switch it replaces. A single WAP could be connected to a switch that is switching multiple IP networks (10.5.x.x and 10.6.x.x) and not care less whether clients of either network use it. Those clients establish their respective TCP/IP configurations independently of the WAP. The only relationship the WAP has to a network is its own. Obviously it must be a member of *some* network for administrative purposes (maybe a third network).
All that said, you do have to be careful. If clients of both IP networks are using the same WAP, then you typically want to avoid having multiple DHCP servers since you never know which one will respond first. That’s not to say you couldn’t have “smart” DHCP servers that only respond to specific MAC addresses and ignore all others. But your basic consumer grade router’s DHCP server isn’t nearly that sophisticated. They will always respond to any request. So if you have multiple DHCP servers of this simplicity, it’s pure chance which one responds first. And that leads to confusion as some clients inevitably end up misconfigured.
So as a practical matter, using the same WAP for multiple IP networks is best avoided. But it’s not prohibited. After all, it’s entirely possible the clients of either network are not using DHCP at all, but completely self-configured.