Reduplication

koaan, koankoaan, koaarn'koankoaan

Duples

You can repeat monosyllable A to get A'A, for some emphasis.

koankoaan (high)
ang'aang (red)
khuikhuy ((adj) opened)
khiuxkhiu (QQ; chewy)
lau-khokkhog, etc (Online Abbreviations)

Triplication

You can repeat a syllable A three times (A"A'A) to mean extremely A. Generally, the first syllable undergoes tone change to the rare rising tone (#6; see Tones of Taiwanese).

aarng'ang'aang
koaarn'koankoaan
loaan'loaxnloan
kaao'kauxkau (厚厚厚; thick)
zeerng'zexngzeng (靜靜靜; quiet)
kiirm'kimkym (kym; 金金金; extremely golden)
khuiie'khuikhuy (開開開; wide open)
thoor'thothoo ( ; to fail/lose completely)
kaao'kaokaux (夠夠夠; very sufficient, see kaokaux)
siirn'sirnsixn (?; ?)
kof'kofkor (古古古; ancient)
leerng'lefnglerng (冷冷冷; extremely cool)
seek'segsek (熟熟熟; very acquainted)
took'togtok (獨獨獨; very alone)
siaap'siapsiab (澀澀澀; very astringent)
siip'sipsib (溼溼溼; very moist. cf. sipsib, sib)