The blade has Katana tapering/curving profile with crude Tsuba, no Habaki abd has Dahb style hilt (and tang

I guessed). This is a good example of Katana-inspired SE asian blades. There is a Japanese record for a trading route between S. Japan and malaya peninsula in the late 16th cent. And in the early 17th cent., Japanese merchants and samurais (mostly ronin

) moved to Siam and established a Japanese settlement in Ayuthaya.
The story is their leader, Yamada Nagamasa (
http://en.wikipedia.org/wiki/Yamada_Nagamasa), got a high position in Ayuthaya. And later, he moved to be a ruler in Nakhon Sri Thammarat (A province in the southern part of Thailand). After the Japanese colony in the Nakorn Sri Thammarat was destroyed by a new king of Siam, many Japanese manged to flee to the Cambodia. And these is the reason why Katana-inspired blades can be found in Cambodia, Central and southern Thailand

.
Any of you having a chance to visit Ayuthaya city should take a look of the still exist Japanese village.