Laos is a multi-ethinic country and each ethnic group has their own their language or dialect. But the official language of Laos is the Lao language as spoken and written in Vientiane. Standard Lao and standard Thai belong to the same linguistic group of the Thai-Kadai language family. The native speakers of Lao standard language and Thai standard language can mutually understand one another thanks to the similarity.
Spoken Lao in Lao People Democratic is recognized as having 5 dialects (and there are many sub-dialects in each dialect): Vientiane Lao, northern Lao, north-eastern Lao, central Lao and southern Lao.
Lao is a tonal language and there are six tones in Vientiane Lao including: Low Tone, Mid Tone, High Tone, Rising Tone, High Falling Tone, Low Falling Tone. Original Lao words are monosyllable-words. Besides, there are many Lao words borrowed from a foreign language such as English, French, Chinese, Pali, Sangkrit...
Lao written language is based on the ancient scripts in southern India, the same as Thai written language. There are 33 consonants, 28 vowels in Lao alphabet. Lao is written and read from left to right.
Other scripts used in Laos include Lao Tham. Tham scripts are commonly used for religious inscriptions.
The transliteration of Lao words into Roman script has lots of problems due to the fact that many sounds in the Lao language can not be represented by the Roman letters. Also the transliteration is often via the Thai-styled pronunciation or through the French language, neither of which is necessarily the same as spoken Lao.
If you plan to travel in Laos independently, it may be useful to pick up a few words before departure. There are many opportunities you can pick up more of the language while touring in the country. If you take an adventure tour in the mountain, then it is very likely that you won’t have to use Lao that much. For those of you who plan to have a long stay in Laos, maybe you should learn the spoken language first, before learning the script.