Is a traffic summons a reportable crime or offence?

I had a traffic summons before to which I pleaded guilty and paid a fine.

Filling out some personnel forms, do I report this as a conviction of crime or offence? as the form requires me to declare it.

Depends on the seriousness of the offense.

if it is minor offense. (In the US called infraction, not sure what the British systems call them) such has speeding, illegal turn, etc., it does not need to be reported. They are not considered criminal offense.

In the US systems, there is an intermediate level offense called misdemeanor, (again, not sure if HK's British modeled legal system have an equivalent.) for convictions such as drunk driving, reckless driving, etc. it would be a judgment call. I would say if the conviction did not come with detention, community service or suspended jail terms, you may not need to disclose. Otherwise, you probably should.

Technically, criminal offense means felony conviction. (again not sure the British term.) Only applies to very serious traffic convictions such as repeated drunk driving, hit and run, reckless endangerment, etc. If you had one of those, it needs to be disclosed.