There are about 6 Android Apps on Google play store related to Khmer dictionaries.

Beside going through to each app, I am first introduce Khmer language to some foreigners since when they come across the apps, some of them keep asking what is “Khmer”. I would first recommend you to read a wiki page about Khmer language, Cambodian language in speaking and writing system.

Chuon Nath Khmer Dictionary by Dreamob

My first recommended app for Khmer to Khmer dictionary to install on your Android phone.
This dictionary is adapted from the original Chuon Nath Khmer Dictionary v2.1.

• 556 rates until now which is 4.7 average rate.
• Size: 2.5MB (Offline), version 1.2, Last update: October 16, 2012
• Free Download

Phum Dictionary (Khmer 3 in 1) by Biz Solutions

Another recommended app is Phum Dictionary which is a 3 in 1 dictionary of Khmer to Khmer, English to Khmer and Khmer to English. This app has a very simple interface and work smoothly on my Galaxy S2.
Features:

• Optimized for LG SmartPhones
• Combine 3 dictionaries: English-Khmer, Khmer-English, Khmer-Khmer (Chuon Nat Dict v2.0)
• Embedded Khmer Unicode for non-LG phones
• Built-in Khmer Keyboard for non-LG phones
• Fast and smart searching
• Comprehensive Definitions

More Info

• 895 rates which is 4.7 totally average.
• Version 2.1, Size: 4.9MB (Offline), Last update on January 27, 2013,
• Free Download

 

English Khmer Dictionary by CNASoft

I rated it as a very simple dictionary is comparing to Phum Dictionary above but just among all dictionaries, I have found this app is released firstly since the Android arrived in Cambodia so even me had installed it as well.
You can try and see since it’s currently has also 839 rates (4.6 overall average rate).
Last update of this app is November 9, 2011.

Features:

• Free for all users
• Support all Android devices
• Very fast
• Easy to use
• Free Download – Size 3.8MB (Offline)

 

Khmer Phrasal Verb Dictionary by Dreamob

A very concise English Khmer phrasal verb dictionary.
Please excuse us in advance if there are some mistakes in Khmer translation. We will try to improve it in each future update. It is a FREE app anyway.

• Total rates: 231, AVG: 4.8
• Version 1.3, Size: 418KB, Last update: May 5, 2012
• Free Download

English-Khmer Phrasal Verbs by R X R Software

Eng-Khmer Phrasal Verb dictionary application delivers the most trusted reference content available. It has the most comprehensive content with a fast, intuitive interface. Providing concise definitions as a quick guide to meaning, the application helps users on matters such as spelling and usage.
Features:

• Instantly look up accurate and extensive definitions and meanings.
• Sample sentences show words in use.
• Size: 477KB, October 1 2012, version 1.2
• Free Download

Taprohm English Khmer Dic by KhmerInnovation

Taprohm English Khmer Dictionary is the largest and most word definitions dictionary for android phone.

It’s a paid dictionary, it’s not free. It’s too old app since April 9, 2011 and remain version 1.0.
It has overall rates of 21 and only 2.8 average rates there are many compains on this app.
If comparing to current free app, I don’t see why we need this one or I might be wrong?
But of course, I haven’t bought it so I don’t know detail about it, if you have it, please tell us about this dictionary in comment.

• Buy at Playstore

 

Conclusion

Per my opinion, I think per now, you can try Phum Dictionary which is 3 in 1 dictionaries so that you do not need to install many apps but if you prefer only one kind of dictionary, just try one another.

Of course, my presume should including as well for how many words are there in each dictionary but I could not find these info yet. I will update later if I found out.