@Lynne ******
Sadly a lot has changed in the last 2 yrs
All Cambodia land borders are closed !
It depends on your history of travel to Thailand over the last 12-18 months
The days of back to back visa exempts - leaving the country and coming back in are done
You can certainly get 60 + days in Thailand , as a tourist , but only if you organise & arrive with the tourist EVisa available online
On the Thai Embassy website from your home country before you come to Thailand