Residents of Ban Si Than can’t leave their work behind when they sleep: this is a pillow-making village. All around the village (and most others surrounding it) you’ll see people sewing, stuffing or selling mŏrn lai kìt (pillows decorated with diamond-grid kìt patterns). The most famous style is a stiff triangle-shaped pillow used as an arm support while sitting on the floor. Most foreigners call these mŏrn kwăhn (axe pillows), though few Thais know this name; mŏrn săhm lĕeam (triangle pillows) is the common moniker.
Truthfully, it's not especially interesting, but prices here are far lower than what you’ll pay elsewhere in Thailand, and this is also one of the few places you can buy them unstuffed (yang mâi sài nûn; literally ‘no kapok inserted’), which makes the big ones viable as souvenirs.
If you want to see monkeys, follow the signs past the village to Don Ling, 5km past the town.
The village is 20km from Yasothon on Rte 202. Any Amnat Charoen–bound bus can drop you at Ban Nikom (25B, 30 minutes), 2.5km north of the village. There are no longer any motorcycle taxis here, so you'll need to walk from there.