The Thai vocabulary consists of a lot of Pali and Sanskrit words. Their spelling is preserved, but not their pronunciation (so that for example, originally dental and retroflex stops except those both voiced and unaspirated become [tʰ] in Thai). However, in a school-level Thai language class, spelling is sometimes taught based on the lost distinction so that students understand consonant combination and redundancy.
I remember being taught that, in a Pali or Sanskrit word, a succession of two stops with the same articulation is either
- geminated unaspirated stops (eg [pp] and [tt]), or
- an unaspirated stop followed by an aspirated counterpart (eg [ppʰ] and [ttʰ]) like in 'buddha' (enlightened) and 'yuddha' (war),
- geminated aspirated stops (eg [pʰpʰ] and [tʰtʰ]), nor
- an aspirated stop followed by an unaspirated counterpart (eg [pʰp] and [tʰt])
This has come up in a discussion between my friend and I, both of whom are native Thai and remember being taught the same thing. And then we question it.
How true is that in Pali and Sanskrit? Are there counterexamples? Could you please point us to an authoritative source regarding this?