Reduplication

Duples

khuikhuy 🔊 (khuy+khuy; 開開; very open)
khiuxkhiu 🔊 (QQ/糗; chewy)
lauxkhokkhog, peh-phauphaw (BPP), suytangtafng, etc. (Online Abbreviations)
tataf 🔊 (taf+taf; very dry)

Triplication

In Taiwanese, triplication refers to repeating a syllable three times for emphasis. For example, "aang" means "red". Something extremely red is "aarng'ang'aang 🔊" (紅紅紅). Generally, the first syllable must undergo tone change to the rare rising tone (#6).

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)
lefng'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 🔊 (sipto; very moist)