Thai and Lao share a similar phonology, being closely related languages, however, several developments occurred in Lao that clearly distinguish them.
Tone, including patterns and quality, is the largest contributing factor and varies widely between varieties of Lao, but together they share splits quite distinct to Ayutthaya dialect (Standard Thai) and other Central Thai dialects. There are also several key sound changes that occurred in the Lao language that differentiates it from Thai.
Consonantal differences Lao lacks the /r/ of formal Thai, replacing it with /h/ or /l/, as well as /tɕʰ/, which is replaced by /s/. Lao also has the consonant sounds /ɲ/ and /ʋ/, which are absent in Thai. Aside from these differences, the consonantal inventory is mostly shared between the two languages.
C1C2 > C1 Unlike Thai, the only consonant clusters that traditionally occur is C/w/, limited in Lao to /kw/ and /kʰw/ but only in certain environments as the /w/ is assimilated into a diphthongization process before the vowels /aː/, /am/, /aːj/ and /a/ thus limiting their occurrence. For example, Isan
kwang (,
kouang, ) is pronounced *
kuang (*, *) but
kwaen as in
kwaen ban (,
khoèn ban, ), 'to feel at home', has a vowel that does not trigger the diphthongization. The consonant clusters of
Proto-Tai had mostly merged in Proto-Southwestern Tai, but clusters were re-introduced with
Khmer,
Sanskrit,
Pali and European loan words, particularly C/l/ and C/r/. Lao simplified the clusters to the first element, but sporadically maintained its orthographic representation as late as the early twentieth century although their pronunciation was simplified much earlier. This was likely an influence of Thai. In some instances, some loan words are sometimes pronounced with clusters by very erudite speakers in formal contexts or in the speech of Isan youth that is very Thaified, otherwise the simplified pronunciation is more common. Lao speakers, especially erudite speakers may write and pronounce
prôkram (, ), via French (), and
maitri (, ) from Sanskrit
maitri (, ) are common, more often than not, they exist as
pôkam (, ) and
maiti (, ), respectively. Similarly, Isan speakers always write and sometimes pronounce, in 'Thai fashion',
maitri (, ) and
prokraem (, ), via English 'programme' or 'program' (US), but most speakers reduce it to and , respectively, in normal speech.
/r/ > /h/ Proto-Southwestern Tai initial
voiced alveolar trill remained [r] in Thai, although it is sometimes pronounced /l/ in informal environments, whereas Lao changed the sound to the
voiceless glottal fricative /h/ in these environments. The sound change likely occurred in the mid-
sixteenth century as the Tai Noi orthography after that period has the letter Lao letter
, which was a variant of /r/ used to record the sound change. The change also included numerous small words of Khmer origin such as
hian , ), 'to learn', which is
rian (, ) in Thai, from Khmer
riĕn (, ).
/r/ > /l/ The shift of Proto-Southwestern Tai */r/ to /h/ in Lao was inconsistent, with some factors that prevented the transition. Instead, these situations led to the shift of /r/ to the
alveolar lateral approximant /l/, similar as to what occurs in informal, casual Thai. Polysyllabic loan words from Khmer as well as Indic sources such as Khmer and Pali may have seemed too 'foreign' compared to the monosyllabic loan words that may have been regarded as native, somewhat similar to English 'beef', ultimately from French
boeuf but fully anglicized in spelling and pronunciation, versus more evidently French loan words such as
crème anglaise, which retains a more French-like pronunciation. Thai speakers sometimes use /l/ in place of /r/ in relaxed, basilectal varieties but this is deprecated in formal speech. •
rasa (
raxa, ) from Sanskrit
rājā (, ), 'king', cf. Thai
racha (, ), 'king' •
raka (, ), 'price' from Sanskrit
rāka (, ), 'wealth', cf. Thai
raka (, ) •
charoen (
chaluen, ), 'prosperity', from Khmer
camraeum (, ), cf. Thai
charoen (, ) •
rabam (, , 'traditional dance', from Khmer
rôbam (, ), cf. Thai
rabam (, ) Lao and Thai both have digraphs, or in the case of Lao ligatures, that consist of a silent /h/ that was historically pronounced at some ancient stage of both languages, but now serves as a mark of tone, shifting the sound to a high-class consonant for figuring out tone. The /h/ may have prevented the assimilation of these words to /h/, as these end up as /l/ in Lao. Similarly, this may have also prevented /r/ to /h/ in Khmer loan words where it begins the second syllable. •
rue (
lu, ) versus
rue (, ), 'or' (conjunction) •
lio (, versus
ri (, ), 'to squint' (one's eyes) •
kamlai (, ), 'profit', from Khmer
kâmrai (, ), cf. Thai
kamrai (, ) •
samrap (
samlap, ), 'for' (the purpose of, to be used as, intended as), from Khmer
sâmrap (, ), cf. Thai
samrap (, ) There are a handful of words where the expected conversion to /h/ did not take place, thus yielding /l/. In some cases, even in the Lao of Laos, this can be seen as historic Siamese influence, but it also may have been conservative retentions of /r/ in some words that resisted this change. For example, Isan has both
hap (, , ) and
lap (, , ), both of which mean 'to receive' and are cognates to Thai
rap (, ), and the
lap variety in Isan and parts of Laos, especially the south, may be due to Thai contact. In other cases, it is because the words are recent loans from Thai or other languages. In Isan, younger speakers often use /l/ in place of /h/ due to
language shift. •
ro (, ), 'to wait, to wait for', cf. Thai
ro (, ) •
rot (
lôt, ), 'car' or 'vehicle', cf. Thai
rot (, ) •
lam (, ), 'to dance', cf. Thai
ram (, ) •
rom (
rôm, ), '
Rome', cf. Thai
rom (, ) •
rangkai (, ) (Isan youth), traditionally
hangkai (, , ), 'body' (anatomic), cf. Thai
rangkai (, )
/tɕʰ/ > /s/ Proto-Tai */ɟ/ and */ʑ/ had merged into Proto-Southwestern Tai */ɟ/, which developed into /tɕʰ/ in Thai, represented by the Thai letter
. Only a small handful of Proto-Tai words with */č/ were retained in Proto-Southwestern Tai, represented by the Tai letter , but this also developed into /tɕʰ/ in Thai and most words with
are either Khmer, Sanskrit or more recent loan words from Chinese dialects, particularly Teochew (Chaoshan Min). Thai also uses the letter which only occurs in a handful of Sanskrit and Pali loan words where it represented /ɟʱ/, but in Thai has the pronunciation /tɕʰ/. Lao has developed /s/ where Thai has /tɕʰ/, with the letter '' /s/, but romanized as 'x', is used to represent cognate words with Thai
or whereas Thai
is replaced by Lao /s/ in analogous environments. Isan speakers will sometimes substitute the Thai letter
/s/ in place of Thai /tɕʰ/ in cognate words, but this is never done to replace
/tɕʰ/ and sometimes avoided in formal, technical or academic word of Khmer, Sanskrit and Pali origins even if the pronunciation is still /s/, although educated Isan speakers and Isan youth may you use /tɕʰ/ due to code-switching or language shift. Similarly, the letter /tɕʰ/ is usually retained even if it is better approximated by tone and phonology by '' /s/ as is done in similar environments in Lao. • Proto-Tai etymon. • Pre-1975 Lao spelling.
/j/ /l/ The Proto-Southwestern Tai cluster *
ml was simplified, producing an expected result of /l/ in Thai and /m/ in Lao. The
Saek language, a
Northern Tai language distantly related to Thai and Lao preserves these clusters. For instance, Proto-Southwestern Tai *
mlɯn, 'to open the eyes', is
mlong in Saek (, , ) but appears as
luem (, ) and
muen (,
mun, ) in Lao.
/w/ > /ʋ/ Lao speakers generally pronounce cognates of Thai with initial /w/ as the
voiced labiodental approximant /ʋ/, similar to a faint 'v', enough so that the French chose 'v' to transcribe the Lao letter
/ʋ/. The letter is related to Thai /w/. The sound /ʋ/ is particularly noticeable in the Vientiane and Central Lao dialects, with a strong pronunciation favored by the élite of Vientiane. In Isan, the rapid but forced resettlement of the people of Vientiane and surrounding areas to the right bank greatly boosted the Lao population, but likely led to some dialect leveling, which may explain the prevalence of /ʋ/ throughout the region, regardless of personal Isan dialect. The replacement is not universal, especially in Laos, but a shift towards /w/ is also occurring in Isan due to the persistent pressures of the Thai language since the sound /ʋ/ is considered provincial, being different from Thai, as opposed to Laos where it is the prestigious pronunciation. Due to the difference in pronunciation, the French-based system used in Laos uses 'v' whereas the English-based Thai system of romanization uses 'w', so the Lao city of Savannakhét would be rendered 'Sawannakhet' if using the Thai transcription.
/k/ > /tɕ/ Another influence of the massive migration of the people of Vientiane to the right bank is the common tendency to replace the
voiceless velar plosive /k/ with the
voiceless alveolo-palatal affricate /tɕ/. For instance, the people of the city of
Khon Chaen, more generally referred to as
Khon Kaen (,
Khon Ken, ) in formal contexts, refer to their city as
Khon Chaen (, *, ) in more relaxed settings. In Laos, this is particularly an informal feature specific to Vientiane Lao but is not used in the official written and spoken standard as it is an informal variant, whereas in Isan, it is commonly used but deprecated as a regional mispronunciation. It is also limited to certain words and environments. }
kaem/
chaem Vocalic differences C/w/ diphthongization Lao innovated a diphthongization that assimilates the /w/ in instances of /kw/ and /kʰw/ in certain environments. This is triggered by the vowels /a/, /aː/, /aːj/ and /am/, but the cluster is retained in all other instances. The /w/ is converted to /u/ and the vowel is shortened to /a/. This is not shown in the orthography, as it must have evolved after the adoption of the
Lao script in the fourteenth century. Cognate words in Lao where this diphthongization occurs have no alteration in spelling from Thai counterparts. For example, the Thai word for 'to sweep' is
kwat (, ) but is
kwat (
kouat, ) and has the suggested pronunciation but is pronounced *
kuat (*
kouat). The counterpart of Thai
khwaen (, ), 'to hang' (something) is also
khwaen (
khwèn, ) since the vowel /ɛː/ does not trigger diphthongization. The vowels /a/, /aː/, /aːj/ and /am/ correspond to Thai
, ,
and and the Lao
, ,
and . The clusters that can undergo this transformation are /kw/, Thai
and Lao or /kw/, Thai '' and ' and Lao
and . The non-diphthongized pronunciations as used in Thai are also used by some Isan speakers as a result of Thai influence. In Laos, non-diphthongization is not incorrect, but may sound like a Thai-influenced
hypercorrection or very pedantic. As it is the normal pronunciation in Laos and Isan, it limits the instances of consonant clusters that are permissible.
/ua/ > /uːə/ The Thai diphthongs and triphthongs with the component /ua/ undergo a lengthening of the /u/ to /uː/ and shortens the /a/ to /ə/, although the shortened diphthong can sound like /uː/ to Thai speakers. In Thai, this includes the vowels /ua/ represented medially by
and finally by , /uaʔ/ by
and the final triphthong /uaj/ by . Lao has /uːə/ represented medially by
and finally by , /uːəʔ/ by
and the final triphthong /uːəj/ by . This may have been another innovation, like C/w/ diphthongization, that occurred after the adoption of writing as it is not represented orthographically.
/ɯ/ > /ɨ/ The
close back unrounded vowel /ɯ/ is centralized to the
close central unrounded vowel /ɨ/ in Lao, which is not found in Thai. This also applies to all variants of /ɯ/ that occur in Thai, i.e., all cognates with instances of Thai /ɯ/ are Lao /ɨ/, including diphthongs and triphthongs that feature this vowel element. Some very traditional dialects of Southern Lao and the Phuan dialect front the vowel all the way to /iː/.
/ɤ/ > /ɘ/ The
close-mid back unrounded vowel /ɤ/ is centralized to the
close-mid central unrounded vowel /ɘ/ in Lao. Similar to the conversion of /ɯ/ to /ɨ/, it also affects all instances in diphthongs as well.
Epenthetic vowels Abugida scripts traditionally do not notate all vowels, especially the short vowel /a/, usually realized as /aʔ/ in Thai and Lao phonology. This especially affects the polysyllabic loan words of Sanskrit, Pali or Khmer derivation. Instances of when or when not to pronounce a vowel have to be learned individually as the presence of the vowel is inconsistent. For example, the Sanskrit word
dharma (, ), which can mean 'dharma', 'moral' or 'justice', was borrowed into Thai as simply
tham ( ). As a root, it appears as simply
tham as in
thammakaset ( ) 'land of justice' or 'righteous land' with the /aʔ/ or
thammanit ( ), 'moral person' with /aʔ/. This is not always justified by etymology, as the terms derive from Sanskrit
dharmakṣetra (, )—actually signifies 'pious man' in Sanskrit—and
dharmanitya (, ), respectively, both of which feature a pronounced but unwritten /a/. Lao and most Isan speakers in relaxed environments will pronounce the 'extra' vowel yielding *
thammakaset (,
thammakasét, ) and
thammanit (, , ). There are also instances where Thai has the epenthetic vowel lost in Lao, such as
krommathan (, ), 'debt contract', whereas Lao has nativized the pronunciation to
kromtham (
kômtham, ). This is an exception, as the extra vowel is a sign of Lao-retained pronunciation such as Thai
chit (, ), 'painting' from Sanskrit
citra (, ), which is
chit (, , ),
chit[
ta] (,
chitta, ) or extremely epentheticized
chit[
tara] (,
chittala, in Isan. As another feature of Isan that deviates from Thai, it is deprecated. Few
Isan people are aware that the stigmatized pronunciations are actually the 'proper' Isan form inherited from Lao. Many of these loan words are limited to academic and formal contexts that usually trigger code-switching to formal Thai, thus Isan speakers may pronounce these words more akin to Thai fashion although to varying degrees of adaptation to Isan pronunciation. Lao speakers also tend to insert epenthetic vowels in normal speech, as opposed to standard Thai where this is less common, thus 'softening' the sentence and making dialogue-less staccato. For instance, the Isan phrase
chak noi (, ), which means 'in just a bit' is often pronounced
chak-ka noy (*จักกะน้อย , cf. Lao *ຈັກກະນ້ອຍ) but this may be perceived as 'slurred' speech to Thai speakers. }}} • Basilectal Isan pronunciation based on historic Lao usage. • 'Lao-ified' pronunciation influenced by formal Thai. • Hypercorrection amongst the educated to approximate Sanskrit pronunciation. ==Grammatical differences==