Kmer language

You can listen and repeat after native khmer.

May be you can learn Khmer in youtube

LINK School of Khmer is a school in Phnom Penh very near to the Independence Monument. It's $4 (or less depending on the plan you carry out) an hour but the first lesson is free. You can find them easily through a Google search

The easiest way is to be born and grow up in Cambodia. It seems to be working well for my Goddaughter. Also a lady here speaks Englisn pretty well and writes the phoenetic on the whiteboard.You will need to go to classified section.

I speak it.
Took 3 months to be able to be understand basic stuff.

Took me about 2 years to have confidence and really understand everything when people spoke quickly.

Carry a small book and write phonetically all words you hear in your basic interaction with Khmers.  When you meet anyone who can interpret and write down the English.
Make a goal of learning 6 words a day.  Linguist's will tell you 300 words will allow you communicate fairly well (= 2 months), 600 you will be almost fluent for everyday basic interaction (= 4 months).

Not sure?  Count all of the words you use to go to the shops, using tuk tuks etc, you will be surprised how few there are.

My advice is don't go to school, you will waste so much time and energy learning words that don't come up often. Learn them down the road.

I have lived here 11 years now.

In my old age I was only able to learn 2 words in 2 days when I was there last month for a very short vacation... But I think I won't forget these new words: bocue (blue) and bitong (green). I seemed to pick up more words easily when I was a bit younger

If you have a smartphone I highly recommend downloading an app  called Convo En-Kh. It comes with hundreds of Cambodian translated words and phrases. Within 2 days I could count to 20 and the locals will appreciate your knowledge.

Tried searching for it on my iPhone. No luck.