Thanks everyone for all the good suggestions.
@hugor very perceptive! I’m in Thailand… 🙂 The crossmarks are good, but a heavy carcase in UST. The surfaces are mostly hardpacked sandy dirt, usually dry, sometimes damp or wet – with a dusting of loose sand off the edges. I’ve ridden at Thetford and it was looser than here.
Just got back from a ride where the front wheel washed out cutting across a bumpy dirt road fast :(. My mistake but maybe the Race Kings as there aren’t many rocks.
The Kenda Small-Block 8s look interesting but there doesn’t seem to be many users.
Rocket Rons look good for grippy cornering and I’ve liked a few Schwalbe tyres.
Another suggestion was WTB TCS Bronson eg 2.1 at 640g – has anyone tried these?