Single-syllable words with a single vowel and one consonant, and if there is a word that has more than 1 syllable must pronounce the syllables (stress) and heavy after another consonant must be added to the 1, then fill ing.
Monosyllable with a single character and a single spell. And if there are words with more than one syllable is pronounced hard (stress), the latter syllable. To add another 1 spell then add ing.
Compounding with สระตัว single and spelling one. And if there is a word with more than 1 syllables. To pronounce syllables after heavy (stress) to increase 1 spelling again. Then add ing.