Hmm A have a small problem - acctually big... My network looks like ths (one of the segments) - Static routing
Clients connected to each AP are in different subnets (as an example below). All APs are in the same subnet(192.168.252.0/24)

clients (192.168.18.0/24)---bridge(wlan1, wlan2 192.168.18.1) ap bridge2 (wlan3, ether 192.168.252.20)----(192.168.252.1)router(213..xx.xxx.xx)

Now I`d like to set public ip some client within 192.168.18.0/24 without using NAT on my main router...

so just create necessary routes on your routers, assign bridge a public IP, that will be the gateway for clients

That`s the problem - Don`t know how to route it. If I set pub ip on AP (bridge where clients connect) and pub ip on clients router with extrenal gw etc I can`t ping anything except that bridge on AP If I set another pub ip tp the second bridge I can`t even ping clients router (mt doesn`to where the clients is connected- two pub ip on two bridges)

what public IPs do you have on the 'router'? your 213.xx.xxx.xx should be routed to you via another address of provider's

if not (if you have default gateway in 213.xx.xxx.xx), then you should play with arp-proxy, I believe