This version of the Lao script is called buddha paṇḍit sabhā chandanapūrī. (อักษรลาวสบับพุทธบัณฑิตสภาจันทน์บูรี) It was created by Dr Mahasila Viravong in 1935.
The goal was to use more letters to write Lao words of Pali and/or Sanskrit origin. Consequently, fourteen letters were added in this edition which are ฆ ฉ ซ ญ ฏ ฐ ฑ ฒ ณ ธ ภ ศ ษ ฬ.
The current government of Laos PDR however does not adopt this edition of the script. The current version used in the republic is highly simplified. Unlike Thai, a large portion of Indic letters are missing, and the spelling does not reflect the etymology of the words.
All letters in this edition have Thai counterparts. Thus, if you can read Thai, reading this version of Lao script will be easy.
Why this script?
There are people who argue that Lao should be written with this version of the script. One of the many people includes the author of "phasa lan xang" by Somchit Phanlak (2012) who wrote the whole book with this script. He along with many scholars argue that there are several good reasons why Lao should be written in this version of the script.
1. etymological spellings and elimination of ambiguities (homophones)
Many argue that this Indic Lao script would eliminate certain ambiguities among some words that are homophonous, i.e. different words that sound the same.
For example, this script would make a distinction among sat ฉัตร (a type of ceremonial umbrella), sat ສັຕວ໌ (animal), and sat ສັຕຍ໌ (honest), whereas the current script used in the republic would spell all these three words the same way: sat ສັດ.
2. people would quickly know the meanings of words
Some people argue that due to the ambiguities engendered by the current script, people are uncertain of names that are important to know. Such words include the name of the capital city of Laos, Vientiane "city of sandalwood", and the names of the speakers themselves which mostly are derived from Pali and/or Sanskrit. People often mistake the city's name for "the city of the moon" because "sandalwood" and "moon" are homophonous in Lao; they are both pronounced as chan (/t͡ɕàn/). If this script was used, different "silent letters" of these two words would disambiguate such ambiguity: "sandalwood" would be spelled ຈັນທນ໌ and "moon" ຈັນທຣ໌. Additionally, some Lao people are not sure what their given names mean. For example, if one's given name was or was composed of wat, he/she might not be sure what his/her name means because wat can mean different things: temple (ວັດ), speech (ວັຈນ໌), feces (ວັຈຈ໌), punishment (ວັຊ), or circle (วัฏ) etc. (Phanlak, 2012)
3. this script would help people learn foreign languages faster
Many argue that the extra letters can be used to write non-Indic foreign words--particularly English, and thus can aid people in learning English or memorizing English spelling. For example, the extra letters will be able to write words such as แลัซ์ "latch" and ฮารธ์ "hearth" (Phanlak, 2012).
There are other arguments in favor of this version by other people. One of them says that if people are write according to how to speak (reflecting their own pronunciations not etymology), there will never be a unified spelling system because there are different Lao dialects with different pronunciations.
Image from the old post