Someone has asked me if I thought pecans would grow and produce nuts in Isaan. I haven't seen them, but maybe you have. I see from a search that they grow in Mexico, Hawaii and Brazil among other tropical and subtropical areas. It's a beautiful tree and a delicious nut. But I suspect that the following will be the primary issues here.

"In Florida, pecan trees can be found in all regions between Pensacola and Miami. Tree growth may be satisfactory in the southern half of the state; however, nut production is usually low because the winters are not cold enough and the higher rainfall increases disease pressure."

You are correct about the temperature. Pecan trees need the cold weather to "go" dormant. Without a dormant season, the tree will bear little to no fruit. The variety found in more "tropical" areas of the U.S. are most likely a grafted tree. The true "native" pecan is small, but very good. There is also the matter of fertilizing the roots and the nuts themselves. The nut has to be fertilized by spraying zinc on the tree. You have all kinds of bugs to worry about when the bloom turns to a nut, although these case bearers are probably not around in Isaan. Then you have to spray for scale during the coldest part of the year. I had many pecan trees and although they was a little work involved, harvested many 1000's lbs of pecans.

I wish there were pecan trees in Thailand, if only for the wood. It make the best BBQ.

As mentioned, cold weather is required for prolific production. The 'native' trees found in the southern states of the US would produce fruit after a mild winter but at, what was usually a reduced yield.

I had several soft shell pecan trees (grafted on native)

The biggest threat to the crop were the crows. They could strip a tree over night it seemed. I used to set in the pecan grove with a shotgun to discourage the winged thieves.

As mentioned, cold weather is required for prolific production. The 'native' trees found in the southern states of the US would produce fruit after a mild winter but at, what was usually a reduced yield.

I had several soft shell pecan trees (grafted on native)

The biggest threat to the crop were the crows. They could strip a tree over night it seemed. I used to set in the pecan grove with a shotgun to discourage the winged thieves.

Mmmmmmm......now dreaming of pecan pie and homemade ice creme.