, indeed, they did last week, for the first time ever. But they were happy when I told them I'd travel to other countries in the region before my 45 days are up. No proof needed in my case.
Tourists holding passports which are on the 45-day visa exempt list don't necessarily need a return ticket. An onward ticket to another country would suffice. In most cases, immigration don't even ask for onward tickets.
, Feb 1st I did a Visa run from Cambodia into Thailand and back to Cambodia at Anlong Veng/Choam painless process on either side, Thai immigration asked nothing of me on entry, but pointed out that I will have only one more entry by land this year on exit back to Cambodia.
No need to carry cash you brought from Thailand during the whole month in Cambodia. You can hit an ATM in Cambodia, get US$. (e.g. At ABA bank with my card I can get up to $500 for a $5 fee, and up to $1000 for a $9 fee). No problem to change $ in THB in the border area.