It's a Peace Lily, Spathiphyllum species. They're from South/Central America and are a very common cultivated plant around the world. There are a lot of hybrids and cultivars available.

Thanks. I'm afraid the leaves don't look like any I have found so far on google. I don't think that Spathiphyllus grows on a trunk?

Is the top picture meant to be the same type of plant as the lower 2? The latter are certainly Spathyphyllums but the top one doesn't look like it to me. Can you show the entire leaves of your plant rather than just the base of the stem?

Of course they are the same plant. I will take some more fotos this week,

You say 'of course' but to me the plant in photo 1 looks entirely different to the plant in photos 3 & 4. For a start it's variegated and the way the leaves are growing at the base looks nothing like a Spathiphyllum. And Spathiphyllums do not grow a 120 cm trunk. If you could just provide a picture of the entire plant from photo 1 rather than just the base of the leaves it would be much easier to id it.

I am very sorry, you are quite right, these are two different plants, my wife took the first two, which are doubtless a Spathiphyllum. She told me it was the same as the one we have at home, which turns out to be a Dieffenbachia. Thanks for letting me waste yout time!

FWIW, I too thought these to be two separate species.

It's the second 2 which are Spathiphyllums. I'd still love to see a complete picture of the first plant because it doesn't look like a Dieffenbachia to me either. I'm really curious about this one because the 'Wilson' part of the Thai name could be a reference to E. H. Wilson, aka 'Chinese Wilson' one of the great plant hunters in SE Asia.

Thanks. After quite some time on internet I found the name Dieffenbachia amoena ‘Wilson’s Delight’ which differs from D. amoena in that the leaves are not variegated

Hooray! We have a result. Thank you so much for continuing this discussion with us and providing more pictures. Now we can see that despite appearances of the base of the pant it isn't variegated. It's been a fascinating puzzle.

How much is this millianor wilson plant worth?

Not a lot, this must be one of the most neglected plants you'll see in Thailand. Maybe $8-10?Wait, wife says that is for TWO plants!