One standard system was devised in the first half of the 20th century when Laos was a French protectorate. There are two important factors that govern the way Lao - as opposed to Thai or Isan - was transcribed in that system. The first is that the Lao script does not render characters that are not pronounced. This standard was put into place via a royal edict, which took the form of a letter from the king to the Comité Littéraire. The idea was both to make it easier for non-ethnic Laotians to read and write Lao, and to differentiate Lao from Thai, which does render characters that are not pronounced. The second factor is that the French system for transcribing sounds was used, hence "ou", for example, instead of "oo" or "u" for an /u/ sound. If not for these two factors, Lao and Thai romanization would appear very similar.
The French transcription system is reflected by the BGN and PCGN standards. (See below.)
The table below shows the Lao consonant letters with their phonetic value in the International Phonetic Alphabet (IPA), and transcriptions according to the US Board on Geographic Names and the British Permanent Committee on Geographical Names (BGN/PCGN), the US Library of Congress (ALA/LC) and the transcriptions used in the Unicode names of the letters.
| character | IPA | BGN/PCGN | ALA/LC | Unicode |
|---|---|---|---|---|
| ກ | k | k | k/k | k |
| ຂ | kʰ | kh | kh/k | kh |
| ຄ | kʰ | kh | kh/k | kh |
| ງ | ŋ | ng | ng/ng | ng |
| ຈ | ʧ | ch | ch/t | c |
| ສ | s | s | s/t | s |
| ຊ | s | x | s/t | s |
| ຍ | ɲ | gn/y | ny/— | ny |
| ດ | d | d/t | d/t | d |
| ຕ | t | t | t/t | t |
| ຖ | tʰ | th | th/t | th |
| ທ | tʰ | th | th/t | th |
| ນ | n | n | n/n | n |
| ບ | b | b/p | b/p | b |
| ປ | p | p | p/p | p |
| ຜ | pʰ | ph | ph/p | ph |
| ຝ | f | f | f/p | f |
| ພ | pʰ | ph | ph/p | ph |
| ຟ | f | f | f/p | f |
| ມ | m | m | m/m | m |
| ຢ | j | y | y | y |
| ຣ | r | r | r | r |
| ລ | l | l | l | l |
| ວ | w | v/o | v | w |
| ຫ | h | h | h | h |
| ອ | — | — | o | |
| ຮ | h | h | h | h |
The table below shows the Lao vowel nuclei, combined with the consonant ກ.
| IPA | BGN | LC | Unicode | IPA | BGN | LC | Unicode | IPA | BGN | LC | Unicode | IPA | BGN | LC | Unicode | ||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ກະ/ກັກ | /a/ | a | a | a | ກາ | /aː/ | a | ā | aa | ||||||||||
| ກິ | /i/ | i | i | i | ກີ | /iː/ | i | ī | ii | ເກັຽະ/ກັຽກ | /iə/ | ia | ia | ເກັຽ/ກຽກ | ia | īa | |||
| ກຶ | /ɯ/ | u | ư | y | ກື | /ɯː/ | u | ư̄ | yy | ເກຶອະ/ເກຶອກ | /ɯə/ | ua | ưa | ເກືອ | ua | ư̄a | |||
| ກຸ | /u/ | ou | u | u | ກູ | /uː/ | ou | ū | uu | ກົວະ/ກັວກ | /uə/ | oua | ua | ກົວ/ ກວກ | oua | ūa | |||
| ເກະ/ເກັກ | /e/ | é | e | ເກ | /eː/ | é | ē | e | |||||||||||
| ແກະ/ແກັກ | /ɛ/ | è | æ | ແກ | /ɛː/ | è | ǣ | ei | |||||||||||
| ໂກະ/ກົກ | /o/ | ô | o | ໂກ | /oː/ | ô | ō | o | |||||||||||
| ເກາະ/ກັອກ | /ɔ/ | o | ǫ | ກໍ/ກອກ | /ɔː/ | o | ǭ | ||||||||||||
| ເກິະ/ເກິກ | /ɤ/ | eu | œ | ເກີ/ ເກືກ | /ɤː/ | eu | œ̄ | ||||||||||||
| ໄກ/ໃກ/ກັຢ | /ai/ | ai | ai | ai/ay | ກາຢ/ກາຽ | /ai/ | āi | ||||||||||||
| ເກົາ | /au/ | ao | ao | ||||||||||||||||
| ກໍາ | /am/ | am | am | am |