How do the Tai words for “sky” differ among Southwestern, Central, and Northern dialects?

In the Tai languages, the word for "sky" serves as a lexical indicator of the relationships between the three primary dialect groups.1

The terminology is distributed as follows:

• Southwestern and Central dialects: These groups share the same root for "sky." For example, it is rendered as fáa in Thai (Southwestern) and faa in Longzhou (Central).1
• Northern dialects: This group uses a distinct term, such as mɯn in Buyei, which is not found in the other two groups.1

This variation in vocabulary is one of the key criteria used by linguists to classify the Tai family into its three distinct branches.21