Does anyone know if the TSA-approved luggage locks that many vendors sell (i.e, TravelSmith, LL Bean) are acceptable in Thailand/Cambodia? I would hate to lock our luggage in the US upon departure only to have people at BKK break it off.

Also, how do you all feel about passport "neck wallets"? Is it better to leave our passports/cash in the hotel safe than carry it on us in one of those security wallets? I used one in Europe and was rather happy with it.

I've used TSA locks world-wide. Remember that other countries don't have the US prohibiton against locking luggage.

I leave my passport as well as any excess cash in the safe in the hotel room.

We used TSA locks in Thailand and Cambodia and had no problems but I don't think that luggage is inspected in the same way in SE Asia as in the USA - there is an initial screening when you get to the airport where you may be required to unlock your luggage but once you get through that I don't believe there is any other screening so the locks don't matter.

I'm a big fan of storing passports in the hotel safe and carrying a photocopy - the wallets are rather cumbersome.

I was in Thaailand and Cambodia earlier this year. I used the TSA locks without incident, as I had done in previous trips.
I strongly recommend leaving passports and cash in hotel safes. I also keep 'emergency money' ($3-400) hidden in a separate place, just in case.
Bankgkok was my last stop on the most recent trip. I ended up using my 'emergency' money to purchase a painting at a place that didn't accept credit cards. So - 'emergency' can have many meanings.......

I carry a color copy of my passport and leave the real one in the hotel safe. I had no problem with TSA locks in Thailand, even with the new restrictions on shampoo, hair gel etc.

we never lock out luggage

Yes, the TSA locks are acceptable in Bangkok and can even be bought at the luggage store in the Paragon mall...I bought one there last month due to TSA having opened my luggage on my L.A.-Tokyo-Singapore-Bangkok flight and then didn't put the locks back on the luggage. My luggage arrived to BK, unlocked. I have a TSA claim form at home to file.
When I got to the airport, in L.A., to leave for my trip, I suddenly realized that I had put on the wrong locks...my old,non-TSA locks. I was furios since I have plenty of TSA locks at home. So I went over to the store in the airport and bought 4 TSA locks...$42.00 and took off the old locks and put on the new ones...and then checked my bag. Well, the locks were missing upon arrival in Bangkok.
THEN...I put on my new TSA lock, bought in Bangkok...and flew Bangkok to Singapore and upon arrival in Singapore, the lock was unlocked, but hanging from my luggage. Maddening!
I always travel with a double set of locks, but since I had left my TSA locks at home, I didn't want to put the old, non-TSA locks on and possibly have them broken off.
If you have a TSA problem, go to tsa.gov. HAppy Travels!

I put TSA locks on my two checked bags from Chicago to Manchester (England)last February. One arrived OK, unopened, the other had been SNIPPED/CUT (ruined the pricey lock), nothing missing, however, I can't imagine that anyone would want my clothes (the only stuff in that bag).