For English speakers, especially Americans, when trying to understand a merging of two (or more) sounds, think of the way in which some people pronounce "which" and "witch" differently and those who do not. In the former case, it is more common among older people. For them, the "wh" in "which" is pronounced like someone is blowing air through a straw. In the latter case on the other hand, the two words are pronounced exactly the same way. Thus for the latter group, the "wh" and "w" have merged into one sound-particularly a "w".
- Kho Khai (ข) and Kho Khuat (ฃ) are pronounced the same way in modern Thai (and many Tai languages including Lao, Shan, Northern Thai, Tai Lue, and Tai Dam).
- In particular, both are pronounced /kʰ/ (but /x/ in Northern Thai and Tai Lue).
- This suggests that in Thai, Kho Khai has replaced Kho Khuat. This may explain why Kho Khuat is now obsolete.
- Historically, Kho Khai and Kho Khuat were pronounced differently.
- Specifically, Kho Khai was pronounced /kʰ/ as the c in cat, and Kho Khuat was pronounced /x/ as the ch in loch in Scottish Gaelic.
- There are two facts that support this claim: (1) The creator of the Thai script had to create the symbols for a reason. The distinction between the two sounds must have caused the creator to create the two symbols, and (2) White Tai, a Tai language spoken in Northern Vietnam, is one of some Tai languages that still have the distinction between the two sounds.
- Tai-Kadai linguists such as Li, Fang Kuei propose that originally Kho Khai was used to represent /kʰ/ while Kho Khuat /x/.