National associations in Thailand often inherit chapter rolls built over decades with different category names, spelling habits, and ideas of what ‘active’ means.
Before comparing chapters, publish a one-page field dictionary: join date, category, status, and chapter code. Ask each chapter to map their labels onto those four fields only.
Resist the urge to demand perfect history on day one. A clean current snapshot beats five years of half-reconciled archives for most council decisions.
Watch for corporate members counted as five people in one chapter and as one entity in another. Agree the counting rule in writing before you draw conclusions about size.
A short quarterly extract in a shared format usually improves chapter comparisons faster than waiting for a single national membership system that may never arrive.