the war ended in 1998 and the only place youre gonna have to worry about mines is up north in thick forested areas near the Thai border and even there you'd be hard pressed to find one.
when will you be going buddy? right now it is the rainy season where Tonle Sap lake has overflown and covered alot of the country up north near Siam Reap. and thats normal. it happens every year. but you should definitely go out and see the floating houses and what not if you go to Angkor. most fishermen out there will double as a sort of tour guide. it ca be sketchy though, so use discretion. keep your money out of sight. theres not necessarily a theft problem but as soon as you pull it out its like a radio beacon.
going anywhere else in SE Asia? hit me up. i live in Singapore and im all over the place here.