Painting done on leaves from Vietnam

These 2 beauties are the size of a coaster and a painted on leaves of some sort.Very talented artist.I can't find any info but think they came from Vietnam bought back to Australia by a soldier in the 60's.
Unfortunately the lady one at top of pic has a texta mark on it due to over zealous pricing at garage sale.These are some of my favourites.The artist appears to be named On
Any info of where to find artist would be appreciated.
larger pic is an oil painting done in vietnam in early 1970's.
Not sure on artist signature it appears to ne Nelson On