I'm going to Thailand next week. Looking for advice on clothing.

I'm very excited to be taking a trip to Thailand with my wife for our honeymoon.

I'm going to do some clothes shopping this week and keen to take advice from those who live in or have travelled to SEA or specifically Thailand before.

I'm going for a minimal approach, so I'll be taking as few clothes as possible and having them laundered whilst I'm there.

For underwear, I'm settled on stocking up on Uniqlo's airism boxers as they're already the most comfortable I've ever owned and I'm certain they'll hold up well to the tropics.

In that vein, I'm not sure if I should also go for the airism t-shirts, or if there's an obviously better choice. I hear lots of mixed opinions on cotton vs merino vs synthetics. I sweat too much for cotton, and have never got on that well with merino (outside of jumpers/sweaters). Given I'll only be there for a couple of weaks, I'm feeling that synthetics are the way to go. But I'm happy to be convinced otherwise.

For footwear I'm going to wear my Altra Escalantes. I'm currently training for a marathon and will have to do at least a few runs while I'm out there, so these will serve as my running shoes and for anywhere I might appreciate plain black shoes (or something more supportive than sandals). Otherwise, I'll be living in my Birkenstock arizonas.

I'll be packing two linen shirts, one linen trousers and then a couple of very lightweight shorts. Again, I'm avoiding cotton with the shorts. I have some ABC WovenAir pull-on shorts from Lululemon that I think will be very comfortable, but I'd be keen for recommendation for another pair or two. I've been told the pacebreakers from Lululemon are great, but not sure if an order from there will arrive on time.

I'm based in the UK, so any recommendations would ideally before for shops we have here, or international brands like Decathlon, Uniqlo, H&M etc.

I understand this is all very personal, but I like hearing different preferences.