Ton Hom Dang ต้นหอม
The red scallion is similar to green onion that it has green top. The bulb is different: red scallions have a pink bulbous bottom instead of a white skinny bottom. They are available at farmers' markets all summer long.
A few years ago, when I first saw red scallions at farmers' markets, I was happy because I could now make a Thai condiment I love. I make pickled red scallions to go with curries and mackerel with chili sauce.