Every serious venue has staff on the bank. They mix bait, set depths, net fish, unhook them, weigh them and take the photograph. They are not there because you are incapable, they are there because these fish need two people and because it is their lake.
Let them work. Visitors who insist on doing everything themselves catch fewer fish, lose more of them, and occasionally hurt one. The person who has netted five thousand catfish knows where to stand.
Tipping is expected but modest. A few hundred baht for a good day with one person looking after you is normal and appreciated. Buy them lunch and a cold drink as well and you will have someone genuinely on your side for the rest of the session. Record claims, if you ever land something that size, go through the International Game Fish Association.
Do not stand on the fish, do not hold anything vertically by the jaw, and do not keep a big fish out of the water while somebody looks for a phone. If a photograph is not ready, the fish goes back and you get another one later.
None of this is complicated and all of it gets noticed. The venues talk to each other, and a visitor with a good reputation gets the better swim next time.