That is a very good overview by Oscar and all 4 main commercial durians in thailand are not a single type.Kradum (button) especially comes in many types with kradum thong the main one.It can be grown further north that the others.
Types are grouped into 3 divisions based on number of days from pollination until picking and there is an assumed relatedness.The ones I really like are montong,gaan yeow,luang and gumpun.They are not simple or alike in flavor.
Many thai durian are grown in Malaysia and have been crossed with Malay types.In MARDI's D nomenclature many are thai types brought to Malaysia decades ago.
Western palates usually find thai varieties more tasty and acceptable.The argument over which are the better quality will never be resolved as it is a question of taste.Oh yeah many tree ripened thai durian are delicious just as many tree ripened Malaysian durian types are.
Okay, here's how I understand the durian situation in Thailand. This info comes straight from an interview I did at the Department of Agriculture in Chanthaburi. They translated a pamphlet for me.
There are five main families of durian. These are:
1. Kop: 47 varieties
2. Luang: 11 varieties, including 4 chanees
3. Ganyao
4. Kampan - 13 varieties
5. Thongyoi - 14 varieties, including Nockyib
Monthong does not belong to any families, and there is no Monthong family. Like puangmanee, monthong is a branded variety/cultivar. It may differ slightly based on soil type, elevation, tree health and pesticide use, but there you have it. Like I said, Monthong is a clone of a single tree.
If someone has information and can prove me wrong, I would appreciate the tip.