Can't say for sure...could be a number of places in SEA, but it reminds me of similar rattan baskets I've seen for knives in Thailand & Burma, but they are usually woven the entire length, but sometimes a large single piece such as this...yours is very nice condition.
Here is a Kachin sword I have that has a basket scabbard...
http://www.vikingsword.com/vb/showthread.php?t=5426