The Japanese filter is depth type.
http://en.wikipedia.org/wiki/Depth_filterThe Thailand filter is surface type.
The depth filter is superior filter in almost all aspects, the only drawback is the cost.
The depth filter can contain substantially more particles before it loses filtering efficiency.
The surface filter will clog up a lot faster, and once it does the oil will simply flow through bypass valve unfiltered.
Basically there is no advantage of using genuine if the genuine is using same filtering method as cheaper brands, providing the quality of construction is similar.
Most likely the Thailand made filter are done at same factory that makes generic branded filters anyway.