The Lao alphabet, Akson Lao (Lao: ອັກສອນລາວ [ʔáksɔ̌ːn láːw]), is the main script used to write the Lao language and other minority languages in Laos. It is ultimately of Indic origin, the alphabet includes 27 consonants (ພະຍັນຊະນະ [pʰāɲánsānā]), 7 consonantal ligatures (ພະຍັນຊະນະປະສົມ [pʰāɲánsānā pá sǒm]), 33 vowels (ສະຫລະ [sálā]) (some based on combinations of symbols), and 4 tone marks (ວັນນະຍຸດ [ván nā ɲūt]). According to Article LXXV of Constitution of the Lao People's Democratic Republic, the Lao alphabet is the official script to the official language, but is also used to transcribe minority languages in the country, but some minority language speakers continue to use their traditional writing systems while the Hmong have adopted the Roman Alphabet. An older version of the script was also used by the ethnic Lao of Thailand's Isan region, who make up a third of Thailand's population, before Isan was incorporated into Siam, until its use was banned and supplemented with the Thai alphabet in 1871, although the region remained distant culturally and politically until further government campaigns and integration into the Thai state (Thaification) were imposed in the 20th century.