The best things to discover in Thailand

In my opinion your question is simply unanswerable.  It is far too broad in scope. You could fill a book with everything you have asked for.

hmmm, I found that in Nakon Sawan, they cam make gootheo, (soup,) with "fish-balls" instead of the usual "pork-balls."  I enjoyed riding a boat through some caves in Trang that you had to lay-down on your back because the roof of the cave was just a couple of millimeters from your nose!  The waterfalls in Loei Province are the most beautiful (for me.)  Erawan Waterfall in Kanchanaburi unfortunately charges Farangs triple the admission price- thereby ruining the entire trip! ....

I go walking every morning at 6am in Jomtien and I really enjoy seeing the lady boys (Katoey) all dressed and made up from the night before.

Understand that exercising people are all in shorts tshirts and runners while these guys are in little black dresses and stiletto shoes, calling out hello handsome man!!!

It is an incredible scene with street sweepers, drunks from the night before, people on mats drinking beers and whisky for breakfast, homeless people, soup carts and then the 6 foot plus lady boys complete with wigs and over the top eye lashes and make up.

I just love the mix and the people.

The best things I have discovered is the peacefulness of the countryside and the acceptance of the people living here with all and everybody and their own life.
There is no jealousy no hate among the people I live with
Their assistance to each other,the food that is shared with all and sundry.The food is not gourmet food but is the tastiest and nicest  that they can afford and make.
The smiles when they see me and my GF  walk in the street or at the local market.
The people going to work early in the morning passing the house and smiling.
Just the whole way of living in Thailand and where I live no crime.
Not having to lock everything away

As per this subject, it's very wide because so many variables based on different people nationalities, age, interests etc

There are places in Thailand or the way Thais do things are so different from other people or countries.

Many westerners come to this part of Asia are amaze or stun or shock or like or hate etc at certain things, behaviour, habits etc that are completely different from them.

Likewise for Asians at western countries are feeling different etc over there.

It's all about individual views and acceptance.

Even certain Asian countries find Thailand and Thais different from their own country in many aspects.

Thailand is backwards especially in smaller cities and villages. There are things well advance in other Asian countries yet Thailand don't know or have it.

Thailand is a lay back country so for many advance countries especiall the west, will find many things to discover.

Villagers smiling at you in the morning is very common in small cities in almost every Asian countries as this has been centuries old.

If you are in Japan even certain districts of Tokyo, you find things left outside the house or shop yet no one steals. Japanese lifestyle and culture is such and they will not do.

I just read the last comment so I don't know what the string is about. But I can say something.

I was at a local Thai shop for about two hours. The owner and I talked while she ran her shop. One take away from that experience is that if you have a good heart then you can enjoy Thailand. There are many differences between Thai culture and the rest of the world, but it is a good culture. If you take things in stride and have a good view point you will find many pleasures with living in Thailand. there are many things that are wrong but there are many things that are not only good but delightful. Enjoy.