توضیحات:

Vietnamese Dictionary plugin for Multiling O Keyboard autocorrect and word prediction

Instruction:
​⑴ Install this plugin and Multiling O Keyboard. https://play.google.com/store/apps/details?id=kl.ime.oh
⑵ Run O Keyboard and follow its setup guide.
⑶ Slide space bar to switch languages.

If you have font issue, read this: http://honsoapps.appspot.com/1/ma.html

Wikipedia:
Vietnamese Listeni/ˌviɛtnəˈmiːz/ (tiếng Việt) is the national and official language of Vietnam. It is the native language of the Vietnamese (Kinh) people, as well as a first or second language for many ethnic minorities of Vietnam. As the result of Vietnamese immigration and cultural influence, Vietnamese speakers are found throughout the world, notably in East and Southeast Asia, North America, Australia and Western Europe.

It is part of the Austroasiatic language family of which it has by far the most speakers (several times as many as the other Austroasiatic languages combined).[7] Vietnamese vocabulary has borrowings from Chinese, and it formerly used a modified set of Chinese characters called chữ nôm given vernacular pronunciation. The Vietnamese alphabet (quốc ngữ) in use today is a Latin alphabet with additional diacritics for tones, and certain letters.