Apologies, I forgot to report on my findings...
I had the chance to try several different brands (but no Merrell). Many were on 25%-40% off sale and wife was wanting to go elsewhere, but I managed 3 hours of trying different boots, from full down through mid to low cut. I had to find something for a walk that was planned this week-end and I wanted to trial something against my current boots. I was also looking for something that might be for Thailand but without any pressure to buy.
I really can't remember the names of everything I tried, nor the market niche for which they were designed. I say this because sometimes something that wasn't designed specifically for a climate can end up being perfect.
I decided that my current pair of Meindl boots were going to be back-up regardless and took the 2-pair and 3-pair sock combinations I use for them. I have a ritual cream/powder/sock combination that I prefer for my feet and bollox to anyone that wants to change that combination..it's seen me happily through 40 years.
After a great deal of deliberation, I decided to procrastinate further over a tropical boot, with preference to the ones I already have. Meanwhile, I would test a pair of Meindl low cut shoes (not sure the name since each of them were the same bar colour in my view when fitting in the shop)...In the end I chose the green grey ones, a 1/2 size bigger than normal, with a name like Ohio...wife has a pair of pink/grey Vegas that she likes (in Germany, never tried in Thailand)
Saturday we went for a 10 hour walk with light packs during warm weather and heavy showers. I wore a 2 sock combination (thin wool inside, thick wool outside) to keep the heel solid in the shoe. We walked on easy tracks, consisting of tarmac, forest path and sand under warm, wet and warm, dry conditions and my feet looked pretty damn good at the end of the day....hot and softened but not bad at all.
Sunday, they were on after shower + talc treatment (no savlon or other foot cream treatments) and they were on for another 10 hours, although only 6hrs for walking. Overall, the lightness of the shoe, together with less than 10Kg pack meant that I didn't tire quite so much during the trip...but I am bloody knackered now...Feet felt sore but on inspection nothing wrong with them and pretty much the same as the previous day.
The shoes were not too bad at all but I would only ever consider them over my boots for light walking over easy terrain. I don't think they would be suitable for walking in Thailand in preference to my current boots. The lack of ankle protection didn't affect me but I would be weary of anything heavier than a light pack.
I tried Mindl Borneo 2 MFS and thought they were too waterproof for humis conditions and too expensive to prove me wrong.
I am going to stick to my stitched leather boots with plenty of room for water to pass each way...and stick to my double wool (summer) combination. I don't think anything I have seen is worth the extra money unless you are walking from Chiang-Mai to Pi-Pi or something similar....