Why Singapore is useful
Singapore is not the largest market, but the rules are structured and official sources are clear. That makes it a good P2 expansion for a precise calculator.
The key product challenge is coverage: overtime entitlement depends on Part IV coverage and salary thresholds.
Recommended cluster
Build a coverage checker first, then a monthly-rated overtime calculator and rest day pay calculator.
This can become a compact country hub without requiring dozens of sub-jurisdiction pages.