Yes I have heard of grafting male and female plants on a rootstock.but haven't seen it being implemented at least in malaysia.maybe it's hard to be done or it has some weakness.btw how do you spell mafai rien in Thai words.i want to search about it on google
pretty sure Mafai Rian (Tong) translates as Golden Coin Mafai, is just a variety of Baccaurea ramiflora lour., a better variety bred for thinner skin, color, etc.
Here is the Thai name: มะไฟเหรียญทอง So generally speaking Mafai Rian Tong is Mafai, and other varieties are not scientifically Mafai, but are still called by Mafai. So that Mafai refers to Baccaurea species as well, such as Mafai Kwai, Mafai Si Daeng, Si Muong (red, purple) etc. This is Thai for Mafai : มะไฟ
มะไฟควาย - Mafai Kwai - Baccaurea macrocarpa
มะไฟกา - Mafai Ga - Baccaurea parviflora
มะไฟแดง - Mafai Daeng - BACCAUREA SCORTECHINII HOOK.F. (same as Mafai Ga?)
มะไฟจำปูลิ่ง - Mafai Jampu Ling - Baccaurea minor
มะไฟลิง - Mafai Ling - Baccaurea polyneura
deep south only:
ละไมป่า - Lamai Pa - Baccaurea bracteata
ละไมลิง - Lamai Ling - Baccaurea javanica
กะดองดอง - Gadongdong - Baccaurea macrophylla
ส้มไฟดิน - Som Fai Din - Baccaurea ptychopyxis
two other Thai ones but not find scientific name, may be another name for one of the varieties above:
มะไฟสีม่วง - Mafai Si Muong - Purple Mafai ??
มะไฟข้าวเหนียวดำ - Mafai Kow Niow Dam - Black Sticky Rice Mafai ??
Credit this website with a lot of the Thai names:
http://my-experimental-farm.blogspot.com/2014/05/blog-post_26.html