What are the important steps and considerations for managing visa overstays in Thailand during a visa run?

Update: bit long winded but trying to cover it all.

I did my Visa run today and maybe of interest.

My wp ran out on 3rd June, my flight was originally to UK for 5th so was told by my Visa organiser to just leave no problem as my non b was stamped till Aug 7th. Well my flight was cancelled and I was given a choice of new dates so did a bit of calculation and decided on 10th July, which she said would still be ok because I was still within my Visa and it wouldn't flag up.

Unfortunately I had to do a 90 day report on the 6th, so went to do it, no problem, got my 90 day report. While there I asked the immigration guy about what happens if my wp runs out before my visa( school boy error) big trouble he says, big fine if I dont renew or cancel my Visa.

So I fessed up thinking I'd be in big trouble when I got to the airport on 10th July and face 35 days overstay. Which it turns out I would be! So I went to the Visa agent, explained the situation and paid 2000 baht for her to cancel my wp. I then went back to the immigration, gave them all the necessary paperwork and got an overstay fine of 2000 baht for 4 days, they stamped my passport till 11th june( today).

Today I went to the chomb chob crossing for Cambodia, after my passport was passed around 4 or 5 officers trying to work out why I had a stamp for 7th Aug and another for today, firstly saying it was a fake stamp and I was 300 days overstay! I explained best I could about what had happened and eventually I was let through. Paid 1500 baht at the first Cambodian desk for the Visa and another 300 baht at the second desk for the stamp. Went over the border no problem, waited 5 min then went to the opposite side and passed through no problem.

Handed my passport to thai immigration, he flicked through it back and forth as over past 5 yr I have amassed quite a few stamps, he asked me if I was planning to work again, and how long I planned to stay, I said 30 days, which I then had to show him proof of my outbound flight, which luckily was booked and was in 30days.

I had the 20k on me just incase I was asked for proof of funds but wasnt asked, he stamped me in till 10th July and through I went.

Had I not cancelled my wp and non b I would defo have been up the creek without a paddle when I got to immigration at bkk on 10th July that is for sure!!

30 days left and back to the UK, where I will apply for the 6 month multi entry Visa for my next trip.