(I'm going to add to this discussion, partly in hopes that one of our linguist experts will pose the question on a professional linguists' board. And partly because, with my key laptop "on the fritz" this is one way for me to create a permanent record!)
First let me say that Thai has no real plural marker. My brain "needs" a plural marker when speaking Thai and I've fallen into the habit of prefixing
พวก - phuak for plural. But this word is actually a noun meaning 'group.' Like many nouns, it is its own classifier so three groups of people would be 'group person three group.'
REDUPLICATION
I think this term includes invented rhyming words, like English "roly-poly" or "easy-peasy." Cockney slang has very complicated patterns. So, although Thai has LOTS of invented rhymes used as slang or colloquially, I don't think that adds much "complexity."
As mentioned, duplicating an adjective is like prefixing "very." Duplicating a noun to make it plural however, is used only in a tiny number of cases I think.
Here's a duplicated word that becomes ambiguous:
ล้านล้าน - lan-lan (million, million)
Conversationally the duplication usually just creates a plural: 'millions.' BUT 'million' is the largest number the language has, so 'thousand million' means 'billion' and 'million million' can also mean 'trillion.'
Instead of rhyming, the initial consonant can be repeated. In each case I show (a) Thai spelling, (b) Romanized rendering per the Royal Institute standard, (c) meaning [in most cases the slangy compound is missing from wiktionary; in some cases it is missing from thai-language.com], (d) definitions for each of the two syllables separately, with "X" denoting absence from both dictionaries.
เยอะแยะ - yoe-yae = many (many, X)
งี่เง่า - ngii-ngao = clumsy, idiot (X, stupid)
เซ่อซ่า - soe-sa = clumsy foolish (foolish, X)
ฟุ่มเฟือย - fum-fueai = extravagant (X, X)
ฟุ้งเฟ้อ - fung-foe = extravagant (to spread, extravagant)
Color words often have a specific suffix applied to mean 'very.' In only the first case ('pee') does the word appear in a dictionary. 'Pee' also means 'very' when prefixed to words for sour, bitter or tight.
ดำปี๋ - dam-pee = very black (black, very*)
แดงแจ๋ - daaeng-jaae = very red (red, X)
ขาวจั๊วะ - khaao-jua = very white (white, X)
'Reuai', which wiktionary translates as 'usually, continuously, always', is often accompanied by a rhyming syllable. (The 'rotten' meaning is not cognate?)
เรื่อยเปื่อย - rueai-pueai = continuously and aimlessly (continuously, rotten)
เรื่อยเบื่อย - rueai-bueai = continuously and aimlessly (continuously, X)
เรื่อยเฉื่อย - rueai-chueai = unhurried (continuously, slow/inert)
เรื่อยเจื้อย - rueai-jueai = on and on without stopping (continuously, X)
เฉย - choei by the way is a near-homonym of
เฉื่อย - chueai and has related meaning. Wiktionary shows etymology for neither.
Finally, here are two common words built by adding a nonsense syllable to 'messy' or 'dirty.' The two words are definitely NOT exact synonyms, but the separate connotations may be dialect-dependent!
เละเทะ - le-the = messy (messy, X)
เลอะเทอะ - loe-thoe = sloppy (dirty, X)