Using your own nameserver names
Most zones should just use ns01.cnx.net.kh. / ns02.cnx.net.kh.. If
you'd rather your NS records show your own domain name instead (for
example ns01.yourdomain.com.), that's supported — it takes two
additional pieces, one in your zone and one at your registrar. See
In-bailiwick nameservers for
why both are needed.
1. In your zone
Add A/AAAA records for your chosen nameserver names, pointing at CNX's anycast addresses:
ns01 IN A 103.237.52.10
ns01 IN AAAA 2001:df6:1440::10
ns02 IN A 103.237.52.11
ns02 IN AAAA 2001:df6:1440::112. At your registrar
Register these same names as glue records (sometimes called "host records" or "child nameservers") pointing at the same addresses. This step happens outside CNX entirely, in your registrar's own control panel.
Not every registrar supports this well, and some ccTLD registries only accept IPv4 glue, not IPv6 — if that's the case for yours, the setup above still works, just without the AAAA glue record.