What this means for learners
Yay and Lao share 28 sounds — roughly 67% of Lao's inventory overlaps with Yay. Shared sounds are ones a speaker already knows from their native language and will generally produce and perceive accurately without explicit training.
The 14 sounds found only in Lao represent the greatest pronunciation challenge for Yay speakers. The adult brain tends to map unfamiliar sounds onto the closest native equivalent — a process that produces the characteristic "accent" of a second-language speaker. Learning to hear and produce these sounds as distinct requires focused ear training, not just repetition.
Conversely, Yay has 10 sounds not used in Lao. Native Lao speakers learning Yay will face the mirror-image challenge with these sounds.
Phoneme inventories from PHOIBLE. Data reflects one documented inventory per language; some variation exists across dialects and sources.