That's essentially a running shoe. A bit thicker sole and more aggressive tread but otherwise a running shoe. That's what I had on my trip. No water resistance. Unknown if there is significant water tolerance. Even if you don't go with Gortex, I would still recommend a proper hiking boot. Maybe something like these:
http://www.rei.com/product/47780667.htm?
vcat=REI_SSHP_FOOTWEAR_TOC
As long as you aren't going someone cold, it probably doesn't matter much if you feet get wet. They will be wet from sweat anyway.
I ran across fire ants 3 times. Twice in Borneo and once in Cambodia. In all three cases, I was wearing sandals so I can't tell you with certainty if mesh is enough. However, I would be very surprised if any stinging insect could penetrate heavy nylon mesh. The 'fire ants' that I encountered don't seem to be nearly as nasty as the ones in the Southern USA. Sharp pain at the time but no blisters or other long term reaction.
In Borneo, the ants were in disturbed rain forest. In Cambodia, it was at an overgrown temple near Preah Kahn. (remote from Kompong Thom, not the one at Angkor). It was rough going in May, at the beginning of the rainy season. When you get to Cambodia, the road will probably be impassible.
The travelogues were posted ages ago. It's just the photos that are taking a long time. I finally finished cleaning up the last of the scans from the Angkor leg yesterday. It will take a few days longer to label